Compilare: user.cpp: In function ‘int main()’: user.cpp:49:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<v.size();i++) if (d[v[i]]==0) {d[v[i]]=1;printf("%d ",v[i]);} ^ user.cpp:41:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bemo.in","r",stdin); ^ user.cpp:42:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bemo.out","w",stdout); ^ user.cpp:44:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d",&n,&m); ^ user.cpp:46:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(j=1;j<=m;j++) {scanf("%d",&a[i][j]);where[a[i][j]]=ii(i,j);} ^