/in/foo.cc: In function 'int main()':
/in/foo.cc:33:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < str.size(); i++){
                  ~~^~~~~~~~~~~~
/in/foo.cc:34:17: warning: comparison with string literal results in unspecified behavior [-Waddress]
   if (str[i] == "1"){
                 ^~~
/in/foo.cc:34:17: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]