Compilare: user.cpp: In function ‘int main(int, const char**)’: user.cpp:17:73: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if( std::count( str.begin(), str.end(), 'A' ) == str.length() ) { ^ user.cpp:24:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, cnt = 0; i < str.length(); i ++ ) { ^ user.cpp:34:53: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0, cnt = 0; i < str.length(); i ++ ) { ^