#include <stdio.h>

int main(int argc, char *argv[])
{
    int p, q, d;
    int j, tot = 0;
    int k, t, a[100000];
    int num;
    char o[1]="";

    principio:

    k = 4000;
    t = 1000;

    printf("\n\nInput number of decimals desired: ");
    scanf(" %i", &tot);

    if (tot%3 != 0)
        tot++;

    printf("\n\n\tPI = 3,");
    num=(tot/3) + 3;

    while(k > 1)
    {
        k--;
        q = 0;
        a[0] += 2;
        p = 1 + 2 * k;

        for(j = 0; j < num; j++)
        {
            if((j > 2 && k == 1) || k == 0)
            {
                d = a[j - 2]%t + (q / p) / t;
                printf("%.3ld",d);
            }
            q = a[j] * k + q%p * t;
            a[j] = q / p;
        }
    }
    tot = (num-3) * 3;

    printf("\n\n\tNumber of decimals: %i", tot);
    printf("\n");
    printf("\n\tWanna try again? (y/n): ");
    scanf(" %c", &o);
    if (o[0]=='y')
        goto principio;

    printf("\n\n");

    return 0;
}