You are given two circles. Find the area of their intersection.

Input

The first line contains three integers x1, y1, r1 ( - 109 ≤ x1, y1 ≤ 109, 1 ≤ r1 ≤ 109) — the position of the center and the radius of the first circle.

The second line contains three integers x2, y2, r2 ( - 109 ≤ x2, y2 ≤ 109, 1 ≤ r2 ≤ 109) — the position of the center and the radius of the second circle.

Output

Print the area of the intersection of the circles. The answer will be considered correct if the absolute or relative error doesn't exceed 10 - 6.

Examples

Input

0 0 4
6 0 4


Output

7.25298806364175601379


Input

0 0 5
11 0 5


Output

0.00000000000000000000
import java.io.*;
import java.awt.geom.*;
import java.text.*;
import java.math.*;
import java.util.*;

public class FD2 implements Runnable {

    final String filename = "";

    MathContext mc = new MathContext(50, RoundingMode.HALF_UP);

    BigDecimal[] sincos(BigDecimal x) {
        BigDecimal s = BigDecimal.valueOf(1, 2); // 0.01
        if (x.compareTo(s) > 0) {
            BigDecimal y = x.divide(BigDecimal.valueOf(2), mc);
            BigDecimal[] siny = sincos(y);
            return new BigDecimal[] { BigDecimal.valueOf(2).multiply(siny[0], mc).multiply(siny[1], mc),
                    siny[1].pow(2, mc).subtract(siny[0].pow(2, mc), mc) };
        }
        BigDecimal sin = BigDecimal.ZERO;
        BigDecimal cos = BigDecimal.ONE;
        BigDecimal mult = x;
        BigDecimal eps = BigDecimal.valueOf(1, mc.getPrecision());
        for (int i = 1; mult.compareTo(eps) > 0; i++) {
            if (i % 2 == 0) {
                if (i % 4 == 0) {
                    cos = cos.add(mult, mc);
                } else {
                    cos = cos.subtract(mult, mc);
                }
            } else {
                if (i % 4 == 1) {
                    sin = sin.add(mult, mc);
                } else {
                    sin = sin.subtract(mult, mc);
                }
            }
            mult = mult.multiply(x, mc).divide(BigDecimal.valueOf(i + 1), mc);
        }
        return new BigDecimal[] { sin, cos };
    }

    BigDecimal f1(BigDecimal a) {
        BigDecimal res = a;
        BigDecimal b = a.multiply(BigDecimal.valueOf(2), mc);
        BigDecimal sin = BigDecimal.ZERO;
        BigDecimal b2 = b.multiply(b, mc);
        BigDecimal mult = b;
        for (int i = 0; i < 20; i++) {
            sin = sin.add(mult, mc);
            mult = mult.multiply(b2, mc);
            mult = mult.divide(BigDecimal.valueOf((2 * i + 2) * (2 * i + 3)), mc).negate();
        }
        return res.subtract(sin.divide(BigDecimal.valueOf(2), mc), mc);
    }

    BigDecimal atan(BigDecimal x) {
        BigDecimal s = BigDecimal.valueOf(1, 1); // 0.1
        int t = 0;
        while (x.compareTo(s) > 0) {
            x = x.subtract(s, mc).divide(BigDecimal.ONE.add(x.multiply(s, mc), mc), mc);
            t++;
        }
        if (t > 0) {
            return atan(s).multiply(BigDecimal.valueOf(t), mc).add(atan(x), mc);
        }
        BigDecimal res = BigDecimal.ZERO;
        BigDecimal mult = x;
        BigDecimal x2 = x.multiply(x, mc);
        int i = 1;
        BigDecimal eps = BigDecimal.valueOf(1, mc.getPrecision());
        while (mult.abs().compareTo(eps) > 0) {
            res = res.add(mult.divide(BigDecimal.valueOf(i), mc), mc);
            mult = mult.multiply(x2, mc).negate();
            i += 2;
        }
        return res;
    }

    public BigDecimal getPi() {
        return BigDecimal.valueOf(4).multiply(atan(BigDecimal.ONE), mc);
    }

    public BigDecimal getPi2() {
        BigDecimal res = atan(BigDecimal.ONE);
        return res.add(res, mc);
    }

    public BigDecimal sqrt(BigDecimal x) {
        int xscale = x.scale();
        int bits = x.unscaledValue().bitLength() + (int) (Math.log(10) * xscale);
        BigDecimal y = new BigDecimal(BigInteger.ONE.shiftLeft(bits / 2), xscale);
        while (true) {
            BigDecimal ny = y.add(x.divide(y, mc), mc).divide(BigDecimal.valueOf(2), mc);
            if (ny.equals(y)) {
                break;
            }
            y = ny;
        }
        return y;
    }

    public BigDecimal atan2(BigDecimal y, BigDecimal x) {
        if (y.signum() > 0 && x.signum() <= 0) {
            return getPi2().add(atan2(x.negate(), y), mc);
        }
        if (y.signum() <= 0 && x.signum() <= 0) {
            return atan2(y.negate(), x).subtract(getPi2(), mc);
        }
        if (y.signum() < 0) {
            return atan2(y.negate(), x).negate();
        }
        if (y.compareTo(x) > 0) {
            return getPi2().subtract(atan2(x, y), mc);
        }
        return atan(y.divide(x, mc));
    }

    public void solve() throws Exception {
        long x1, y1, r1;
        long x2, y2, r2;
        x1 = iread();
        y1 = iread();
        r1 = iread();
        x2 = iread();
        y2 = iread();
        r2 = iread();
        long d2 = (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
        if (d2 >= (r1 + r2) * (r1 + r2)) {
            out.write("0\n");
            return;
        }
        if (d2 <= (r1 - r2) * (r1 - r2)) {
            BigDecimal r = BigDecimal.valueOf(Math.min(r1, r2));
            BigDecimal res = r.multiply(r, mc).multiply(getPi(), mc);
            out.write(res + "\n");
            return;
        }
        BigDecimal r1sq = BigDecimal.valueOf(r1).pow(2, mc);
        BigDecimal r2sq = BigDecimal.valueOf(r2).pow(2, mc);
        BigDecimal dsq = BigDecimal.valueOf(d2);
        BigDecimal ix1 = r1sq.subtract(r2sq, mc).add(dsq, mc);
        BigDecimal iy2 = BigDecimal.valueOf(r1 + r2).pow(2, mc).subtract(dsq, mc)
                .multiply(dsq.subtract(BigDecimal.valueOf(r1 - r2).pow(2, mc), mc), mc);
        BigDecimal iy = sqrt(iy2);
        BigDecimal a1 = atan2(iy, ix1);
        BigDecimal res = r1sq.multiply(f1(a1), mc);
        BigDecimal ix2 = r2sq.subtract(r1sq, mc).add(dsq, mc);
        BigDecimal a2 = atan2(iy, ix2);
        res = res.add(r2sq.multiply(f1(a2), mc), mc);
        System.out.println(res);

    }

    DecimalFormat df = new DecimalFormat("0.000000");

    public void run() {
        try {
            in = new BufferedReader(new InputStreamReader(System.in));
            out = new BufferedWriter(new OutputStreamWriter(System.out));
            // in = new BufferedReader(new FileReader(filename+".in"));
            // out = new BufferedWriter(new FileWriter(filename+".out"));
            solve();
            out.flush();
        } catch (Exception e) {
            e.printStackTrace();
            System.exit(1);
        }
    }

    public int iread() throws Exception {
        return Integer.parseInt(readWord());
    }

    public double dread() throws Exception {
        return Double.parseDouble(readWord());
    }

    public long lread() throws Exception {
        return Long.parseLong(readWord());
    }

    BufferedReader in;

    BufferedWriter out;

    public String readWord() throws IOException {
        StringBuilder b = new StringBuilder();
        int c;
        c = in.read();
        while (c >= 0 && c <= ' ')
            c = in.read();
        if (c < 0)
            return "";
        while (c > ' ') {
            b.append((char) c);
            c = in.read();
        }
        return b.toString();
    }

    public static void main(String[] args) {
        try {
            Locale.setDefault(Locale.US);
        } catch (Exception e) {

        }
        // new Thread(new Main()).start();
        new Thread(null, new FD2(), "1", 1 << 25).start();
    }
}