pblv2018

import java.math.BigDecimal;
import java.math.MathContext;
import java.math.RoundingMode;

public class Chudnovski {

    static final int LIMIT = 2;

    public static void main(String[] args) {

        MathContext mc = new MathContext(5000, RoundingMode.HALF_UP);

        BigDecimal sum = new BigDecimal(0).setScale(50, RoundingMode.HALF_UP);

        for (int k = 0; k < LIMIT; k++) {
            BigDecimal dividend = new BigDecimal(Math.pow(-1, k) * faculty(6 * k) * (545140134 * k + 13591409))
                    .setScale(50, RoundingMode.HALF_UP);
            BigDecimal divisor = new BigDecimal(Math.pow(faculty(k), 3) * faculty(3 * k) * Math.pow(640320, 3 * k))
                    .setScale(50, RoundingMode.HALF_UP);

            BigDecimal increment = (dividend.divide(divisor, mc)).setScale(50, RoundingMode.HALF_UP);
            System.out.println("inc: " + increment);

            sum = sum.add(increment).setScale(50, RoundingMode.HALF_UP);
            System.out.println("sum: " + sum);
        }

        BigDecimal pi = new BigDecimal(426880 * Math.sqrt(10005)).divide(sum, mc).setScale(50, RoundingMode.HALF_UP);

        System.out.println(pi);
        System.out.println(Math.PI);

    }

    private static long faculty(int i) {
        if (i <= 1) {
            return 1L;
        } else {
            return i * faculty(i - 1);
        }
    }

}