Compilare: user.cpp: In function ‘void bck(std::vector<std::pair<int, int> >)’: user.cpp:63:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < npct.size(); i++) ^ user.cpp: In function ‘int main()’: user.cpp:106:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < pct.size(); i++) ^ user.cpp:89:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("immortal.in", "r", stdin); ^ user.cpp:90:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("immortal.out", "w", stdout); ^ user.cpp:93:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &N, &M, &K); ^ user.cpp:97:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^