Compilare: user.cpp: In function ‘int solve(std::vector<std::pair<int, int> >)’: user.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=1; i<a.size(); ++i) ^ user.cpp:30:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<b.size(); ) ^ user.cpp:33:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<b.size() && b[i].first<=u) ^ user.cpp: In function ‘int main()’: user.cpp:42:43: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("carpetbomber.in", "r", stdin); ^ user.cpp:43:45: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("carpetbomber.out", "w", stdout); ^ user.cpp:45:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:49:39: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &type, &X, &Y); ^