Problem: 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

Solution (in PYTHON3):

Solution:
#!/usr/bin/env python3
# 600D_circles.py - Codeforces.com/problemset/problem/600/D by Sergey 2015

import unittest
import sys
import math
import decimal

###############################################################################
# Circles Class (Main Program)
###############################################################################


def sin(x):
    decimal.getcontext().prec += 2
    i, lasts, s, fact, num, sign = 1, 0, x, 1, x, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    decimal.getcontext().prec -= 2
    return +s


def cos(x):
    decimal.getcontext().prec += 2
    i, lasts, s, fact, num, sign = 0, 0, 1, 1, 1, 1
    while s != lasts:
        lasts = s
        i += 2
        fact *= i * (i-1)
        num *= x * x
        sign *= -1
        s += num / fact * sign
    decimal.getcontext().prec -= 2
    return +s


def pi():
    decimal.getcontext().prec += 2
    three = decimal.Decimal(3)
    lasts, t, s, n, na, d, da = 0, three, 3, 1, 0, 0, 24
    while s != lasts:
        lasts = s
        n, na = n+na, na+8
        d, da = d+da, da+32
        t = (t * n) / d
        s += t
    decimal.getcontext().prec -= 2
    return +s


def asin(x):
    decimal.getcontext().prec += 2
    b, e = -pi()/2, pi()/2
    while True:
        mid = (b + e) / 2
        if e == mid or b == mid:
            break
        if sin(mid) <= x:
            b = mid
        else:
            e = mid
    decimal.getcontext().prec -= 2
    return +b


def acos(x):
    return pi() / 2 - asin(x)


class Circles:
    """ Circles representation """

    def __init__(self, test_inputs=None):
        """ Default constructor """

        it = iter(test_inputs.split("\n")) if test_inputs else None

        def uinput():
            return next(it) if it else sys.stdin.readline().rstrip()

        # Reading single elements
        [self.xa, self.ya, self.ra] = map(decimal.Decimal, uinput().split())
        [self.xb, self.yb, self.rb] = map(decimal.Decimal, uinput().split())

        decimal.getcontext().prec = 40

        self.l = ((self.xb - self.xa)**2 + (self.yb - self.ya)**2).sqrt()
        self.p = (self.ra + self.rb + self.l)/2

        if self.l >= self.p:
            self.sa = 0
            self.sb = 0
        elif self.ra >= self.p:
            self.sa = 0
            self.sb = self.rb**2 * decimal.Decimal.from_float(math.pi)
        elif self.rb >= self.p:
            self.sa = self.ra**2 * decimal.Decimal.from_float(math.pi)
            self.sb = 0
        else:
            self.aa = 2 * acos(
                (self.ra**2 - self.rb**2 + self.l**2) /
                (2 * self.ra * self.l))
            self.ab = 2 * acos(
                (self.rb**2 - self.ra**2 + self.l**2) /
                (2 * self.rb * self.l))
            self.sa = self.ra**2 * (self.aa - sin(self.aa)) / 2
            self.sb = self.rb**2 * (self.ab - sin(self.ab)) / 2

    def calculate(self):
        """ Main calcualtion function of the class """

        result = self.sa + self.sb

        return str(result)

###############################################################################
# Unit Tests
###############################################################################


class unitTests(unittest.TestCase):

    def test_single_test(self):
        """ Circles class testing """

        # Constructor test
        test = "0 0 4\n6 0 4"
        d = Circles(test)
        self.assertEqual(d.l, 6)

        # Sample test
        self.assertEqual(Circles(test).calculate()[:8], "7.252988")

        # Sample test
        test = "0 0 5\n11 0 5"
        self.assertEqual(Circles(test).calculate(), "0")

        # Sample test
        test = "44721 999999999 400000000\n0 0 600000000"
        self.assertEqual(Circles(test).calculate()[:9], "0.0018834")

        # My tests
        test = ""
        # self.assertEqual(Circles(test).calculate(), "0")

        # Time limit test
        # self.time_limit_test(5000)

    def time_limit_test(self, nmax):
        """ Timelimit testing """
        import random
        import timeit

        # Random inputs
        test = str(nmax) + " " + str(nmax) + "\n"
        numnums = [str(i) + " " + str(i+1) for i in range(nmax)]
        test += "\n".join(numnums) + "\n"
        nums = [random.randint(1, 10000) for i in range(nmax)]
        test += " ".join(map(str, nums)) + "\n"

        # Run the test
        start = timeit.default_timer()
        d = Circles(test)
        calc = timeit.default_timer()
        d.calculate()
        stop = timeit.default_timer()
        print("\nTimelimit Test: " +
              "{0:.3f}s (init {1:.3f}s calc {2:.3f}s)".
              format(stop-start, calc-start, stop-calc))

if __name__ == "__main__":

    # Avoiding recursion limitaions
    sys.setrecursionlimit(100000)

    if sys.argv[-1] == "-ut":
        unittest.main(argv=[" "])

    # Print the result string
    sys.stdout.write(Circles().calculate())