using System;
using static System.Console;
using static System.Math;

public class main{
static int nx=0;
static double acc=1e-10;
static double eps=0;

public static double erf(double z){
	if(z<0)return -erf(-z);
	Func<double,double> f = x => {nx++; return Exp(-x*x);};
	double q;
	if(z<1.25) {
		q= 2/Sqrt(PI)*integrate.quad(f,0,z,acc:acc,eps:eps);
		}
	else {
		Func<double,double> F = t => f(z+(1-t)/t)/t/t;
		q= 1-2/Sqrt(PI)*integrate.quad(F,0,1,acc:acc,eps:eps);
		}
Error.WriteLine($"z={z:f6} npoints={nx}");
	nx=0;
	return q;
	}

public static void Main(){
	for(double z=-3; z<=3; z+=1.0/8)
		Console.WriteLine($"{z} {erf(z)}");

        WriteLine("\n");
        WriteLine("-2   -0.995322265");
        WriteLine("-1   -0.842700793");
        WriteLine("-0.5 -0.520499878");
        WriteLine("-0.2 -0.222702589");
        WriteLine(" 0.2  0.222702589");
        WriteLine(" 0.5  0.520499878");
        WriteLine(" 1    0.842700793");
        WriteLine(" 2    0.995322265");

	}


}//main