/in/foo.cc: In function 'int main()':
/in/foo.cc:7:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0; i<s.size(); i++)
                ~^~~~~~~~~
/in/foo.cc:8:18: error: 't' was not declared in this scope
   if (s[i]=='1') t++;
                  ^
/in/foo.cc:9:10: error: 't' was not declared in this scope
  cout << t << endl;
          ^
/in/foo.cc:5:6: warning: unused variable 'tot' [-Wunused-variable]
  int tot=0;
      ^~~