need some help with pi() func!!!!!!

i need to build a basic program that print the num pi....
output: 3.0000000000
what is wrong??

Code:

# include <stdio.h>
double long exp1(double base, unsigned long exp)
{
    double sum=1;
    unsigned long i;
    for (i=0; i<exp; i++)
    {
        sum=sum*base;
    }
    return sum;
}
double long pi(int k)
{
    double long sum=0;
    if (k==0)
    {
        sum=(47/15);
        return sum;
    }
    sum=((1/(exp1(16,k)))*((4/((8*k)+1))-(2/((8*k)+4))-(1/((8*k)+5))-(1/((8*k)+6)))) + pi(k-1);
    return sum;
}
int main()
{
    int k=0;
    printf("please enter how many k of pi do you like\n");
    scanf_s("%d",&k);
    
    if (k<0)
    {
        while (k<0)
        {
            printf("please enter positive number\n");
            scanf_s("%d",&k);
        }
    }
    printf("the number is %.10lf\n",pi(k));
    return 0;
}

The biggest problem I see is all the integer math. Remember when using integer math there are no fractions. So sum=(47/15); would evaluate to 3 not 3.1333333, 1/2 would evaluate to zero not .5.

Jim

When using integer fraction will be truncated.
Solution:add .0 extentions for integer(example:47.0/15) or type casting it(example:sum=(float(47),15)).
Sorry my english is very bad!.

I realize that you're trying to compute it in a very specific way, but FWIW, a very simple and useful equivalence to remember is PI == 4 * atan(1).

Your function declarations are wrong. You mean long double not double long.
Didn't your compiler complain about this?

thank's guys....