Compilare: user.cpp: In function ‘int main()’: user.cpp:24:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<b.size()&&i<1000;i++) out<<b.at(i)<<" "; ^ user.cpp:15:17: warning: unused variable ‘M’ [-Wunused-variable] int i=0,I=1,M=m.length(),N=n.length(); ^ user.cpp:15:30: warning: unused variable ‘N’ [-Wunused-variable] int i=0,I=1,M=m.length(),N=n.length(); ^