#include <fstream>
#include <iostream>

using namespace std;

int main()
{
    ofstream a_file ( "pi.txt" );
    int digits;
    float summation = 0.0;
    float pi_approx = 0.0;
    
    cout<<"Number of digits of pi: "<<endl;
    cin>>digits;
    
    for (int count=0; count <= digits; count++) {
        summation = summation + (((-1^count)*((-32/(4*count)+1)-(1/(4*count)+3)+(256/(10*count)+1)-(64/(10*count)+3)-(4/(10*count)+5)-(4/(10*count)+7)+(1/(10*count)+9)))/(1024^count));
    }
    
    pi_approx = summation * (1/64);
    
    a_file<<pi_approx;
    cin.get();
    
    system("PAUSE");
    return 0;
}