factorial of 13 code example

Example 1: calculate factorial

int factorial(int n) {
	int res = 1, i; 
    for (i = 2; i <= n; i++) 
        res *= i; 
    return res; 
}

Example 2: factorial

unsigned long long factorial(unsigned long long num){

    if(num<=0)
        return 1;

    return num * factorial(num-1);
}