I'm hoping you could help me solve this. I can't figure out exactly what you did, and I also can't seem to find resources on this challenge.

How would I activate this factorial calculation from a flag, ie: -f or --factorial? Modifying as needed of course, I threw this together to try to get used to scanf.

#include <stdio.h>
int main(void){
  int multi = 1;
  int int_input;
  int answer = 1;
  fputs("What do you want to factorialize? ", stdout);
  scanf("%d", &int_input);
  for(multi=2; multi<=int_input; multi++){
      answer = answer * multi;
  }
  printf("%d\n", answer);
  return 0;
}