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.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        DAreaOfTwoCirclesIntersection solver = new DAreaOfTwoCirclesIntersection();
        solver.solve(1, in, out);
        out.close();
    }

    static class DAreaOfTwoCirclesIntersection {
        private static final int ITER = 1_00_000_000;

        public void solve(int testNumber, InputReader in, PrintWriter out) {
            double x1 = in.nextDouble(), y1 = in.nextDouble(), r1 = in.nextDouble();
            double x2 = in.nextDouble(), y2 = in.nextDouble(), r2 = in.nextDouble();
            if (Math.abs(x1 - x2) < Math.abs(y1 - y2)) {
                double t = x1;
                x1 = y1;
                y1 = t;
                t = x2;
                x2 = y2;
                y2 = t;
            }

            double xmin = Math.max(x1 - r1, x2 - r2);
            double xmax = Math.min(x1 + r1, x2 + r2);
            double x0 = (xmin + xmax) / 2;
            double y0 = (y1 + y2) / 2;
            xmin -= x0;
            xmax -= x0;
            x1 -= x0;
            x2 -= x0;
            y1 -= y0;
            y2 -= y0;

            double area = 0;
            double STEP = (xmax - xmin) / ITER;
            double prevL = -1;
            for (double x = xmin; x < xmax; x += STEP) {
                double dy1 = r1 * r1 - (x - x1) * (x - x1);
                dy1 = dy1 <= 0 ? 0 : Math.sqrt(dy1);
                double a1 = y1 - dy1, b1 = y1 + dy1;

                double dy2 = r2 * r2 - (x - x2) * (x - x2);
                dy2 = dy2 <= 0 ? 0 : Math.sqrt(dy2);
                double a2 = y2 - dy2, b2 = y2 + dy2;

                double l = Math.min(b1, b2) - Math.max(a1, a2);
                if (l <= 0)
                    l = 0;
                if (prevL == -1)
                    prevL = l;
                area += (l + prevL) / 2;
                prevL = l;
            }
            area *= STEP;

            out.println(area);
        }

    }

    static class InputReader {
        public final BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public double nextDouble() {
            return Double.parseDouble(next());
        }

    }
}

