police.cpp: In function 'void dfs(int, int)': police.cpp:24: warning: comparison between signed and unsigned integer expressions police.cpp: In function 'int main()': police.cpp:67: warning: comparison between signed and unsigned integer expressions police.cpp:68: warning: comparison between signed and unsigned integer expressions police.cpp:69: warning: comparison between signed and unsigned integer expressions police.cpp:46: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result police.cpp:47: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result police.cpp:49: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result police.cpp:53: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result