#include <iostream>
#include <cmath>
using namespace std;
int main()
{
cout << "erf(-1) = " << erf(-1) << endl;
cout << "erf(1) = " << erf(1) << endl;
cout << "erf(0) = " << erf(0) << endl;
cout << "erf(-0) = " << erf(-0) << endl;
return 0;
}
/*
run:
erf(-1) = -0.842701
erf(1) = 0.842701
erf(0) = 0
erf(-0) = 0
*/