Compilare: main.cpp: In function 'int main()': main.cpp:30:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j = 0 ; j < G[v[i].y].size() ; j ++) ~~^~~~~~~~~~~~~~~~~~ main.cpp:18:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("tester.in", "r", stdin); ^ main.cpp:19:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("tester.out", "w", stdout); ^ main.cpp:21:28: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d" , &n , &m); ^ main.cpp:24:34: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d" , &tx , &ty); ^