float firstTerm = 4/1;
    float sign = 1;

    for (float i = 3; i <= 100000000; i += 2)
    {
        //cout << setprecision(20) << i << endl;
        sign *= -1;
        firstTerm += sign *(4/i);
    }

    cout << "pie to 20 significant figures:     ";
    cout << setprecision(20) << firstTerm << endl;


    //cout << setprecision(20) << 1.0 / 3.0;



    int i = 0;
    cin >> i;


    return 0;