/in/foo.cc: In function 'long long int change(std::__cxx11::string)':
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<s.size();i++){
               ^
/in/foo.cc: In function 'long long int gcd(long long int, long long int)':
/in/foo.cc:16:12: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  while(r=a%b){
            ^