Compilare: user.cpp: In function ‘int main()’: user.cpp:41:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<s.size();i++) ^ user.cpp: In function ‘long long int recursiv(long long int)’: user.cpp:37:1: warning: control reaches end of non-void function [-Wreturn-type] } ^