#include <STDIO.H>
long fact(int n);
long rfact(int n);
int main(void)
{
 int num;
 printf("This program calculates factorials.\n");
 printf("Enter a value in the range 0-12 (q to quit):\n");
 while(scanf("%d",&num)==1)
 {
 if(num<0)
  printf("No negative numbers,please.\n");
 else if (num>12)
 {
  printf("Keep input under 13.\n");
 }
 else
 {
  printf("loop:%d factorial=%d\n",num,fact(num));
  printf("recursion:%d factorial=%d\n",num,rfact(num));
 }
 }
}

long fact(int n)
{
 long ans;
 for (ans=1;n>1;n--)
 {
 ans*=n;
 }
 return ans;
}

long rfact(int n)
{
 long ans;
 if (n>0)
 {
 ans=n*rfact(n-1);
 } 
 else
 {
 ans=1;
 }
 return ans;
}