foo.c: In function 'main':
foo.c:9:10: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[10001]' [-Wformat=]
  scanf("%s\n%s",&num1,&num2);
         ~^      ~~~~~
foo.c:9:14: warning: format '%s' expects argument of type 'char *', but argument 3 has type 'char (*)[10001]' [-Wformat=]
  scanf("%s\n%s",&num1,&num2);
             ~^        ~~~~~
foo.c:24:8: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
  while(ans[max]=0) max--;
        ^~~
foo.c:9:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%s\n%s",&num1,&num2);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~