/in/foo.cc: In function 'int main()':
/in/foo.cc:49:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < ans.length(); i++)
                    ~~^~~~~~~~~~~~~~
/in/foo.cc:62:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = flag; i <= ans.length(); i++)
                           ~~^~~~~~~~~~~~~~~
/in/foo.cc:44:9: warning: unused variable 'len1' [-Wunused-variable]
     int len1 = num1.length();
         ^~~~
/in/foo.cc:45:9: warning: unused variable 'len2' [-Wunused-variable]
     int len2 = num2.length();
         ^~~~