diff --git a/src/fast_cal/cal_core.cc b/src/fast_cal/cal_core.cc
index 94944e9..039c10c 100644
--- a/src/fast_cal/cal_core.cc
+++ b/src/fast_cal/cal_core.cc
@@ -39,24 +39,26 @@ void FastCal::new_case(uint64_t code, uint64_t mask) {
 }
 
 /// found first matched target
-uint64_t FastCal::target(uint64_t code, const check_t &match) {
-    auto core = init(code);
-    while (!cache.empty()) { // bfs search
+RawCode FastCal::target(RawCode code, const check_t &match) {
+    auto core = init((uint64_t)code);
+    /// start bfs search
+    while (!cache.empty()) {
         if (match(cache.front()->code)) {
-            return cache.front()->code; // match target
+            return RawCode::unsafe_create(cache.front()->code); // match target
         }
         core.next_cases(cache.front()->code, cache.front()->mask);
         cache.pop();
     }
-    return FastCal::NOT_FOUND; // target not found
+    return FC_NOT_FOUND; // target not found
 }
 
 /// found multi-targets matched in first same layer
-std::vector<uint64_t> FastCal::target_multi(uint64_t code, const check_t &match) {
-    auto core = init(code);
+std::vector<RawCode> FastCal::target_multi(RawCode code, const check_t &match) {
+    auto core = init((uint64_t)code);
     auto layer_end = cache.back();
-    std::vector<uint64_t> matched; // matched list
-    while (!cache.empty()) { // bfs search
+    std::vector<RawCode> matched; // matched list
+    /// start bfs search
+    while (!cache.empty()) {
         if (match(cache.front()->code)) { // match target
             matched.emplace_back(cache.front()->code);
         }
@@ -69,17 +71,20 @@ std::vector<uint64_t> FastCal::target_multi(uint64_t code, const check_t &match)
         }
         cache.pop();
     }
-    return std::vector<uint64_t>{}; // no target found
+    return std::vector<RawCode>{}; // no target found
 }
 
 /// found all of the furthest cases
-std::vector<uint64_t> FastCal::furthest(uint64_t code) {
-    auto core = init(code);
+std::vector<RawCode> FastCal::furthest(RawCode code) {
+    auto core = init((uint64_t)code);
     auto layer_end = cache.back();
-    std::vector<uint64_t> layer_cases;
-    while (!cache.empty()) { // bfs search
+    std::vector<RawCode> layer_cases;
+    /// start bfs search
+    while (!cache.empty()) {
         core.next_cases(cache.front()->code, cache.front()->mask);
-        layer_cases.emplace_back(cache.front()->code); // record layer cases
+        layer_cases.emplace_back(
+            RawCode::unsafe_create(cache.front()->code) // record layer cases
+        );
         if (cache.front() == layer_end) { // reach layer ending
             if (cache.size() == 1) {
                 break; // stop loop at last layer
diff --git a/src/fast_cal/fast_cal.cc b/src/fast_cal/fast_cal.cc
index f18b53a..7a0d180 100644
--- a/src/fast_cal/fast_cal.cc
+++ b/src/fast_cal/fast_cal.cc
@@ -7,13 +7,13 @@
 #include <iostream>
 #include <algorithm>
 
-uint64_t FastCal::solve(uint64_t code) {
+RawCode FastCal::solve(RawCode code) {
     return FastCal::target(code, [](uint64_t code) {
         return ((code >> (3 * 0xD)) & 0b111) == B_2x2; // check 2x2 block address
     });
 }
 
-std::vector<uint64_t> FastCal::solve_multi(uint64_t code) {
+std::vector<RawCode> FastCal::solve_multi(RawCode code) {
     return FastCal::target_multi(code, [](uint64_t code) {
         return ((code >> (3 * 0xD)) & 0b111) == B_2x2; // check 2x2 block address
     });
diff --git a/src/fast_cal/fast_cal.h b/src/fast_cal/fast_cal.h
index cf1cd5d..46b3f2f 100644
--- a/src/fast_cal/fast_cal.h
+++ b/src/fast_cal/fast_cal.h
@@ -4,22 +4,29 @@
 #include <vector>
 #include <cstdint>
 #include <unordered_map>
+#include "raw_code.h"
+
+/// FastCal not found -> return invalid raw code
+const RawCode FC_NOT_FOUND = RawCode::unsafe_create(0);
 
 class FastCal {
 public:
     const static auto NOT_FOUND = (uint64_t)0;
     typedef std::function<bool(uint64_t)> check_t;
 
+//    const static RawCode *test = (RawCode*)nullptr;
+
     /// xxx_multi only search until same layer
 
     // TODO: shall we use RawCode instead of uint64_t?
 
-    uint64_t solve(uint64_t code);
-    uint64_t target(uint64_t code, const check_t &match);
+    RawCode solve(RawCode code);
+    RawCode target(RawCode code, const check_t &match);
+
+    std::vector<RawCode> furthest(RawCode code);
 
-    std::vector<uint64_t> furthest(uint64_t code);
-    std::vector<uint64_t> solve_multi(uint64_t code);
-    std::vector<uint64_t> target_multi(uint64_t code, const check_t &match);
+    std::vector<RawCode> solve_multi(RawCode code);
+    std::vector<RawCode> target_multi(RawCode code, const check_t &match);
 
     // TODO: search / search_multi / resolve / resolve_multi
     // TODO: static furthest function
diff --git a/src/main.cc b/src/main.cc
index 948c28d..2759ee3 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -27,9 +27,16 @@ int main() {
 
     auto f = FastCal();
 //    auto ret = f.solve((uint64_t)RawCode::from_common_code("1a9bf0c"));
-    auto ret = f.solve((uint64_t)RawCode::from_common_code("1a9bf0c"));
+//    auto ret = f.solve(RawCode::from_common_code("1a9bf0c"));
+    auto ret = f.solve(RawCode::from_common_code("1aaef0c"));
 
-    std::cout << f.step_num(ret) << std::endl;
+    if (ret == FC_NOT_FOUND) {
+        std::cout << "not found" << std::endl;
+    } else {
+        std::cout << ret << std::endl;
+    }
+
+//    std::cout << f.step_num(ret) << std::endl;
 
 //    auto f = FastCal(RawCode::from_common_code("1a9bf0c").unwrap());
 //    auto ret = f.solve();
diff --git a/src/raw_code/raw_code.cc b/src/raw_code/raw_code.cc
index 611ca91..719a293 100644
--- a/src/raw_code/raw_code.cc
+++ b/src/raw_code/raw_code.cc
@@ -6,6 +6,10 @@ uint64_t RawCode::unwrap() const {
     return code; // raw uint64_t code
 }
 
+bool RawCode::valid() const {
+    return RawCode::check(code);
+}
+
 RawCode RawCode::create(uint64_t raw_code) {
     return RawCode(raw_code);
 }
@@ -23,6 +27,10 @@ RawCode::RawCode(uint64_t raw_code) {
     code = raw_code;
 }
 
+bool RawCode::operator==(const RawCode &raw_code) const {
+    return this->code == raw_code.code;
+}
+
 std::ostream& operator<<(std::ostream &out, const RawCode &self) {
     char code[16];
     char dump_map[] = {
diff --git a/src/raw_code/raw_code.h b/src/raw_code/raw_code.h
index 65a7907..54dc37c 100644
--- a/src/raw_code/raw_code.h
+++ b/src/raw_code/raw_code.h
@@ -9,7 +9,11 @@ class CommonCode;
 
 class RawCode {
 public:
+    bool valid() const;
     static bool check(uint64_t raw_code);
+
+    /// Operators of RawCode
+    bool operator==(const RawCode &raw_code) const;
     explicit operator uint64_t() const { return code; }
     friend std::ostream& operator<<(std::ostream &out, const RawCode &self);