Compilare: user.cpp: In function ‘int main()’: user.cpp:30:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < g[a].size(); ++i) ^ user.cpp:54:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < g[a].size(); ++i) ^ user.cpp:13:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.in", "r", stdin); ^ user.cpp:14:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("graf.out", "w", stdout); ^ user.cpp:17:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &n, &m, &x, &y); ^ user.cpp:20:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &a, &b); ^