Compilare: user.cpp: In function ‘int find_match(int)’: user.cpp:20:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a[u].size();++i) ^ user.cpp: In function ‘int main()’: user.cpp:76:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<res.size();++i) printf("C %d %d\n",res[i].first,res[i].second); ^ user.cpp:47:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("revolutie.in","r",stdin); ^ user.cpp:48:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("revolutie.out","w",stdout); ^ user.cpp:50:19: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ user.cpp:54:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&k); ^