Compilare: main.cpp: In function 'void dfs(int, int)': main.cpp:34:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0 ; j < G[u].size() ; j ++) ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:56:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.in" , "r" , stdin); ^ main.cpp:57:42: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("biconex.out" , "w" , stdout); ^ main.cpp:59:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d" , &n , &m); ^ main.cpp:62:32: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d" , &u , &v); ^