Compilare: user.cpp: In function ‘bool pairUp(int)’: user.cpp:21:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < G[N].size(); i++) { ^ user.cpp:29:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < G[N].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:40:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("java.in", "r", stdin); ^ user.cpp:41:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("java.out", "w", stdout); ^ user.cpp:43:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &T); ^ user.cpp:45:39: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d%d", &NL, &NR, &M); ^ user.cpp:48:35: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d", &x, &y); ^