Compilare: user.cpp: In function ‘void back(long long unsigned int, int)’: user.cpp:24:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(nr%m==0 && nr<nrm && nr>=m) ~~^~~ user.cpp: In function ‘int cmmdc(int, int)’: user.cpp:19:1: warning: control reaches end of non-void function [-Wreturn-type] } ^