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

double myatan(double x){
	int k, N=10;
	double Sum=0.0, t=-1.0/x, dx;
	for (k=0; k<=N; k++){
		t *= -1.0*x*x;
		dx = t/(2*k+1);
		Sum += dx;
	}
	return Sum;
}

int main(void){
	printf("4*myatan(1) = %.15f\n",4*myatan(1.));
	printf("4*atan(1) = %.15f\n",4*atan(1.));
	printf("Machin: %.15f\n",4*(4*myatan(1./5)-myatan(1./239)));
	printf("Takano: %.15f\n",4*(12*myatan(1./49)+32*myatan(1./57)-5*myatan(1./239)+12*myatan(1./110443)));
	return 0;
}