Compilare: user.cpp: In function ‘int main()’: user.cpp:17:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<s.size(); ++i) ^ user.cpp:28:19: warning: statement has no effect [-Wunused-value] ok==0; ^ user.cpp:48:19: warning: statement has no effect [-Wunused-value] ok==0; ^ user.cpp:12:16: warning: unused variable ‘n’ [-Wunused-variable] int ok, k, n; ^