Compilare: user.cpp: In function ‘int r()’: user.cpp:69:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<st.size(); j++) ^ user.cpp: In function ‘int main()’: user.cpp:118:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i< s.size(); i++) ^ user.cpp:137:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<s.size(); i++) ^