diff --git a/klotski/common.cc b/klotski/common.cc
index 8118f23..13bc5a6 100644
--- a/klotski/common.cc
+++ b/klotski/common.cc
@@ -37,36 +37,3 @@ bool Common::check_case(uint32_t head, uint32_t range) { // whether the head and
     }
     return true; // valid case
 }
-
-bool Common::check_case_safe(uint32_t head, uint32_t range) { // whether the case is valid
-    uint32_t space_num = 0;
-    uint32_t mask = 0b110011 << head; // fill 2x2 block
-    for (int addr = 0; range; range >>= 2) { // traverse every 2-bits
-        while (mask >> addr & 0b1) {
-            ++addr; // search next not filled block
-        }
-        switch (range & 0b11) {
-            case 0b00: // space block
-                ++space_num;
-            case 0b11: // 1x1 block
-                if (addr > 19) { // invalid address
-                    return false;
-                }
-                mask |= 0b1 << addr; // fill 1x1 block
-                break;
-            case 0b10: // 2x1 block
-                if (addr > 15 || mask >> (addr + 4) & 0b1) { // invalid address
-                    return false;
-                }
-                mask |= 0b10001 << addr; // fill 2x1 block
-                break;
-            case 0b01: // 1x2 block
-                if (addr > 18 || (addr & 0b11) == 0b11 || mask >> (addr + 1) & 0b1) { // invalid address
-                    return false;
-                }
-                mask |= 0b11 << addr; // fill 1x2 block
-                break;
-        }
-    }
-    return space_num >= 2; // at least 2 space
-}
diff --git a/klotski/common.h b/klotski/common.h
index 505bef1..8c80a6c 100644
--- a/klotski/common.h
+++ b/klotski/common.h
@@ -6,5 +6,4 @@ class Common {
 public:
     static uint32_t range_reverse(uint32_t bin);
     static bool check_case(uint32_t head, uint32_t range);
-    static bool check_case_safe(uint32_t head, uint32_t range);
 };
diff --git a/klotski/common_code.cc b/klotski/common_code.cc
index e4e403d..75b9fbd 100644
--- a/klotski/common_code.cc
+++ b/klotski/common_code.cc
@@ -3,9 +3,29 @@
 
 bool CommonCode::check(uint64_t common_code) {
     uint32_t head = common_code >> 32;
-    auto range = (uint32_t)common_code;
     if (head >= 16 || (head & 0b11) == 0b11) { // check 2x2 block address
         return false; // invalid common code
     }
-    return Common::check_case_safe(head, Common::range_reverse(range)); // check by head and range
+
+    uint32_t fill_num = 0, space_num = 0;
+    auto range = Common::range_reverse((uint32_t)common_code); // get common code range
+    for (int i = 0; i < 32; i += 2) { // traverse range
+        switch ((range >> i) & 0b11) {
+            case 0b00: // space block
+                ++space_num;
+            case 0b11: // 1x1 block
+                ++fill_num;
+                break;
+            case 0b01: // 1x2 block
+            case 0b10: // 2x1 block
+                fill_num += 2;
+        }
+        if (fill_num >= 16) { // all block filled
+            break;
+        }
+    }
+    if (space_num < 2) {
+        return false; // at least 2 space
+    }
+    return Common::check_case(head, range); // check by head and range
 }
diff --git a/klotski/main.cc b/klotski/main.cc
index 4b1f2dd..408e1a0 100644
--- a/klotski/main.cc
+++ b/klotski/main.cc
@@ -46,28 +46,29 @@ int main() {
 //    }
 
 //    uint32_t sum = 0;
-//    for (uint32_t head = 0; head < 1; ++head) {
-//        auto prefix = (uint64_t)head << 32;
-//        for (uint64_t range = 0; range < 0x100000000; ++range) {
-//            uint64_t code = prefix | range;
-//            if (CommonCode::check(code)) {
-//                printf("%09lX\n", code);
+    for (uint32_t head = 0; head < 16; ++head) {
+        auto prefix = (uint64_t)head << 32;
+        for (uint64_t range = 0; range < 0x100000000; ++range) {
+            uint64_t code = prefix | range;
+            if (CommonCode::check(code)) {
+                printf("%09lX\n", code);
 //                ++sum;
-//            }
+            }
 //            if (range % 0x1000000 == 0) {
 //                std::cout << range / 0x1000000 << std::endl;
 //            }
-//        }
-//    }
+        }
+    }
 //    std::cout << "sum: " << sum << std::endl;
 
-    uint64_t error_code = 0x02EFFF7C0;
+//    uint64_t error_code = 0x02EFFF7C0;
+//    uint64_t error_code = 0x07B4EFC00;
 
-    if (CommonCode::check(error_code)) {
-        std::cout << "true" << std::endl;
-    } else {
-        std::cout << "false" << std::endl;
-    }
+//    if (CommonCode::check(error_code)) {
+//        std::cout << "true" << std::endl;
+//    } else {
+//        std::cout << "false" << std::endl;
+//    }
 
     return 0;
 }