#include <stdio.h>
#include <math.h>
int main (void)
{ double e, pi;
double funpi (double e);
printf ("Enter e:");
scanf ("%lf", &e);
pi = funpi (e);
printf ("pi = %f\n", pi);
return 0;
}
double funpi (double e)
{ int denominator, flag;
double item, sum;
flag = 1;
denominator = 1;
item = 1.0;
sum = 0;
while (fabs (item) >= e){
item = flag * 1.0 / denominator;
sum = sum + item;
flag = -flag;
denominator = denominator + 2;
}
return sum * 4;
}