police.cpp: In function 'void bfs(int)': police.cpp:20: warning: comparison between signed and unsigned integer expressions police.cpp: In function 'void dfs1(int)': police.cpp:34: warning: comparison between signed and unsigned integer expressions police.cpp: In function 'void dfs2(int)': police.cpp:45: warning: comparison between signed and unsigned integer expressions police.cpp: In function 'int main()': police.cpp:67: warning: unused variable 's' police.cpp:68: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result police.cpp:69: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result police.cpp:70: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result police.cpp:72: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result