Factorial

#include <stdio.h>
#include <stdlib.h>

void main()
{
    while (1)
    {
     int n,i,product=1;
    printf("Enter value: ");
    scanf("%d",&n);
    if (n>0)
    {
        for (i=n;i>0;i--)
        {
            product*=i;
        }
        printf("Factorial = %d\n",product);
    }
    else if (n==0)
        printf("Factorial = 1\n");
    else
        printf("Undefined value\n");
    }

}