Compilare: main.cpp: In function 'int main()': main.cpp:31:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j=0;j<v1[i].size();j++) ans[++l]=v1[i][j].second; ~^~~~~~~~~~~~~ main.cpp:10:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("calorifer.in","r",stdin); ^ main.cpp:11:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("calorifer.out","w",stdout); ^ main.cpp:13:19: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&n); ^ main.cpp:14:44: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] for(int i=1;i<=n;i++) scanf("%d",&v[i]); ^