Calculate factorial value of any number using awk command

BEGIN
 { main(); }
 function main()
 { facto(); }
 function facto()
 {
  printf("\n Enter The Number: ");
  getline n;
  fact=1;
  for(i=n;i>1;i--)
  fact=fact*i;
  printf("\nFactorial of %d is %d",n,fact);
 }