/in/foo.cc: In function 'int main()':
/in/foo.cc:7:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < str.size(); ++i){
                    ~~^~~~~~~~~~~~
/in/foo.cc:18:18: warning: 'm' may be used uninitialized in this function [-Wmaybe-uninitialized]
     cout << m << " " << n << " " << sum;
                  ^~~
/in/foo.cc:18:30: warning: 'n' may be used uninitialized in this function [-Wmaybe-uninitialized]
     cout << m << " " << n << " " << sum;
                              ^~~