#include<stdio.h>

int fact1(int n) {
  if (n<2) return 1; else return n*fact1(n-1);
}

int fact2(int n, int ax) {
  if (n<2) return ax; else return fact2(n-1, n*ax);
} // pass 1 to ax initially

int fact3(int n) {
  int ax = 1;
  while (n>=2) {
    ax = n*ax;
    n -= 1;
  }
  return ax;
}

int main() {
  return 0;
}