Compilare: user.cpp: In function ‘int main()’: user.cpp:35:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<M.size(); i++) ~^~~~~~~~~ user.cpp:24:19: warning: unused variable ‘ok’ [-Wunused-variable] int n,m,i,a,b,ok,nr=0; ^~ user.cpp:24:22: warning: unused variable ‘nr’ [-Wunused-variable] int n,m,i,a,b,ok,nr=0; ^~ user.cpp:44:9: warning: unused variable ‘nod’ [-Wunused-variable] int nod=1; ^~~