Compilare: user.cpp: In function ‘int main()’: user.cpp:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(;r.size()<n; r+='a'); ^ user.cpp:34:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(r.size()>n) cout<<"-1\n"; ^ user.cpp:25:9: warning: variable ‘ok’ set but not used [-Wunused-but-set-variable] int ok=1; ^