In file included from /in/Compile/check.cpp:7:
/in/sokoban.hpp:201:56: error: implicit conversion changes signedness: 'int' to 'size_t' (aka 'unsigned long') [-Werror,-Wsign-conversion]
        process_horizontal(grid, visited, boundary, i, -1); // 上方
        ~~~~~~~~~~~~~~~~~~                             ^~
/in/sokoban.hpp:207:54: error: implicit conversion changes signedness: 'int' to 'size_t' (aka 'unsigned long') [-Werror,-Wsign-conversion]
        process_vertical(grid, visited, boundary, j, -1); // 左侧
        ~~~~~~~~~~~~~~~~                             ^~
2 errors generated.
/in/Compile/Makefile:16: recipe for target 'main' failed
make: *** [main] Error 1