Compilare: user.cpp: In function ‘void solve()’: user.cpp:129:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < pairs.size() - 1; ++i) ^ user.cpp: In function ‘int main()’: user.cpp:157:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("plan.in","r",stdin); ^ user.cpp:158:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("plan.out","w",stdout); ^ user.cpp:160:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:164:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^