#include<stdio.h>
long factorial(int);
int main()
{
int n;
long f;
printf("Enter an integer to find factorial\n");
scanf("%d", &n);
if (n < 0)
printf("Negative integers are not allowed.\n");
else
{
f = factorial(n);
printf("%d! = %ld\n", n, f);
}
return 0;
}
long factorial(int n)
{
if (n == 0)
return 1;
else
return(n * factorial(n-1));
}
