diff --git a/src/main.cc b/src/main.cc
index 21066d6..e0f1acb 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -362,14 +362,14 @@ int main() {
 //    printf("%09lX\n", CommonCode::from_string("1a9bf0c").unwrap());
 //    std::cout << CommonCode("4feA134") << std::endl;
 
-    std::vector<uint64_t> all_cases;
-    for (uint64_t head = 0; head < 16; ++head) {
-        for (const auto &range : AllCases::fetch()[head]) {
-            all_cases.emplace_back(head << 32 | range);
-        }
-    }
-    std::cout << "test size: " << all_cases.size() << std::endl;
-
+//    std::vector<uint64_t> all_cases;
+//    for (uint64_t head = 0; head < 16; ++head) {
+//        for (const auto &range : AllCases::fetch()[head]) {
+//            all_cases.emplace_back(head << 32 | range);
+//        }
+//    }
+//    std::cout << "test size: " << all_cases.size() << std::endl;
+//
 //    for (const auto &common_code : all_cases) {
 //        if (RawCode::compact(RawCode::extract(common_code)) != common_code) {
 //            std::cout << "Error: " << CommonCode(common_code) << std::endl;
@@ -382,12 +382,27 @@ int main() {
 
 //    std::cout << RawCode::check(CommonCode(0x4FEA13400).to_raw_code().unwrap()) << std::endl;
 
-    for (const auto &common_code : all_cases) {
-        if (!RawCode::check(RawCode::extract(common_code))) {
-            std::cout << "Error: " << CommonCode(common_code) << std::endl;
-        }
-    }
+//    for (const auto &common_code : all_cases) {
+//        if (!RawCode::check(RawCode::extract(common_code))) {
+//            std::cout << "Error: " << CommonCode(common_code) << std::endl;
+//        }
+//    }
+
+//    for (uint64_t common_code = 0; common_code < 0x100000000; ++common_code) {
+//    for (uint64_t common_code = 0x555A4000; common_code < 0x100000000; ++common_code) {
+//        if (RawCode::check(RawCode::extract(common_code)) != CommonCode::check(common_code)) {
+//            printf("%09lX\n", common_code);
+//        }
+//        if (common_code % 0x1000 == 0) {
+//            std::cout << std::hex << common_code << std::endl;
+//        }
+//    }
 
+    // TODO: why 0x555a4001 broken extract function?
+//    std::cout << RawCode(RawCode::extract(0x00000FEC4)).dump_case() << std::endl;
+//    std::cout << RawCode(RawCode::extract(0x000055480)).dump_case() << std::endl;
+//    std::cout << RawCode(RawCode::extract(0x0000FF004)).dump_case() << std::endl;
+    std::cout << RawCode::extract(0x555a4001) << std::endl;
 
 //    std::cerr << (clock() - start_time) * 1000 / CLOCKS_PER_SEC << "ms" << std::endl;
     std::cerr << (clock() - start_time) * 1000000 / CLOCKS_PER_SEC << "us" << std::endl;
diff --git a/src/raw_code/convert.cc b/src/raw_code/convert.cc
index eebb6eb..178fc0e 100644
--- a/src/raw_code/convert.cc
+++ b/src/raw_code/convert.cc
@@ -47,6 +47,8 @@ uint64_t RawCode::compact(uint64_t raw_code) { // raw code --> common code
     return head | (range << (unfilled << 1)); // fill low bits as zero
 }
 
+#include <iostream>
+
 /// NOTE: ensure that input common code is valid !!!
 uint64_t RawCode::extract(uint64_t common_code) { // common code --> raw code
     auto code = C_2x2 << (common_code >> 32) * 3; // flag for 2x2 block
@@ -55,6 +57,13 @@ uint64_t RawCode::extract(uint64_t common_code) { // common code --> raw code
         while (0b111 & code >> addr) { // check low 3-bits -> next empty address
             addr += 3; // found available address
         }
+
+        // TODO: remove after test
+        if (addr >= 60) {
+            return 0;
+        }
+//        std::cout << "addr = " << addr << " | block = " << (range & 0b11) << std::endl;
+
         switch (range & 0b11) { // match low 2-bits
             case 0b01: // 1x2 block
                 code |= C_1x2 << addr;
diff --git a/src/raw_code/raw_code.cc b/src/raw_code/raw_code.cc
index dfb8b99..1d5c9c7 100644
--- a/src/raw_code/raw_code.cc
+++ b/src/raw_code/raw_code.cc
@@ -27,6 +27,21 @@ std::string RawCode::dump_case() const {
 }
 
 bool RawCode::check(uint64_t raw_code) { // check whether raw code is valid
+    constexpr uint64_t MASK_1x1 = ~B_1x1 & 0b111;
+    constexpr uint64_t MASK_1x2 = MASK_1x1 << 3;
+    constexpr uint64_t MASK_2x1 = MASK_1x1 << 12;
+    constexpr uint64_t MASK_2x2 = MASK_1x1 << 3 | MASK_1x1 << 12 | MASK_1x1 << 15;
+
+//    if (MASK_1x2 != 0b100000) {
+//        printf("error\n");
+//    }
+//    if (MASK_2x1 != 0b100000000000000) {
+//        printf("error\n");
+//    }
+//    if (MASK_2x2 != 0b100100000000100000) {
+//        printf("error\n");
+//    }
+
     if (raw_code >> 60) {
         return false; // high 4-bits must be zero
     }
@@ -43,17 +58,20 @@ bool RawCode::check(uint64_t raw_code) { // check whether raw code is valid
                 if (addr > 15 || (raw_code & F_2x1) != C_2x1) {
                     return false; // invalid 2x1 block
                 }
+                raw_code &= ~MASK_2x1; // B_fill -> B_1x1
                 continue;
             case B_1x2:
                 if ((addr & 0b11) == 0b11 || (raw_code & F_1x2) != C_1x2) {
                     return false; // invalid 1x2 block
                 }
+                raw_code &= ~MASK_1x2; // B_fill -> B_1x1
                 continue;
             case B_2x2:
                 ++head_num;
                 if (addr > 14 || (addr & 0b11) == 0b11 || (raw_code & F_2x2) != C_2x2) {
                     return false; // invalid 2x2 block
                 }
+                raw_code &= ~MASK_2x2; // B_fill -> B_1x1
                 continue;
             default:
                 return false; // unknown flag -> 0b101 / 0b110