#include <stdio.h>
#include <math.h>

int main() {
    float pi = 0, absadd, precision, add, middle, end_pi;
    int n, i = -1;
    printf("Enter number of digits (1-7): ");
    scanf("%d", &n);

    precision = pow(0.1, n);

    do
    {
        i++;
        add = 4*pow(-1, i)/(2*i+1);
        pi += add;
        absadd = fabs(add);
    } while (absadd>=precision);

    middle = -(add/2);
    printf("step    %d\n",i);
    pi += middle;
    end_pi = (float)(((int)(pi*pow(10,n)))/pow(10,n));
    printf("   pi = %.*f\n\n",n,end_pi);
    return 0;
}