Compilare: user.cpp: In function ‘bool makepair(int)’: user.cpp:20:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for ( int i=0;i<v[x].size();++i ) ^ user.cpp: In function ‘int main()’: user.cpp:30:22: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&n); ^ user.cpp:34:30: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(f,"%d",&x); ^