/in/foo.cc: In function 'int main()':
/in/foo.cc:12:8: warning: unused variable 'flag' [-Wunused-variable]
    int flag=0;
        ^~~~
/in/foo.cc:23:24: warning: format '%d' expects argument of type 'int', but argument 2 has type '__gnu_cxx::__enable_if<true, double>::__type {aka double}' [-Wformat=]
  printf("%d",abs(s2-s1));
                        ^