Factorial using User define function

#include<stdio.h>
int fact(int );
int main()
{
	long int a,res;
	printf("Enter any number to calculate its factorial:\t");
	scanf("%ld",&a);
	res=fact(a);
	printf("\nFACTORIAL IS:\t %ld",res);
	getch();
	return 0;
}
int fact(int a)
{
	if(a==0||a==1)
	return 1;
	if(a>=2)
	return a*fact(a-1);
}