Compilare: main.cpp: In function 'void solve()': main.cpp:52:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<edges.size(); ++i) if(vis[edges[i].first]!=vis[edges[i].second]) sol.push_back(i+1); ~^~~~~~~~~~~~~ main.cpp: In function 'void read()': main.cpp:24:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("critice.in", "r", stdin); ^ main.cpp:25:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ main.cpp:28:36: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x, &y, &c); ^ main.cpp: In function 'void write()': 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("critice.out", "w", stdout); ^