/in/foo.cc: In function 'int main()':
/in/foo.cc:27:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  if(a.length()<maxn)for(ll i=a.length();i<maxn;i++)a="0"+a;
     ~~~~~~~~~~^~~~~
/in/foo.cc:40:21: warning: format '%ld' expects argument of type 'long int', but argument 2 has type 'll {aka long long int}' [-Wformat=]
  printf("%ld",answer);
                     ^