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
from decimal import Decimal, getcontext

class Trigonometry():
    def __init__(self, precision):
        getcontext().prec = precision
        self.pi = self._pi_()

    def _pi_(self):
        lo, hi = Decimal('3.14'), Decimal('3.15')
        while True:
            mid = (lo + hi) / 2
            if mid == lo or mid == hi:
                break
            if self.sin(mid) < 0:
                hi = mid
            else:
                lo = mid
        return lo

    def sin(self, x):
        res = x
        xpow = x
        fact = Decimal(1)
        k = 3
        while True:
            xpow *= -x * x
            fact *= k * (k - 1)
            next = res + xpow / fact
            if res == next:
                break
            res = next
            k += 2
        return res

    def cos(self, x):
        res = Decimal(1)
        xpow = Decimal(1)
        fact = Decimal(1)
        k = 2
        while True:
            xpow *= -x * x
            fact *= k * (k - 1)
            next = res + xpow / fact
            if res == next:
                break
            res = next
            k += 2
        return res

    def exp(self, x):
        res = Decimal(1)
        xpow = Decimal(1)
        fact = Decimal(1)
        k = 1
        while True:
            xpow *= x
            fact *= k
            next = res + xpow / fact
            if res == next:
                break
            res = next
            k += 1
        return res

    def acos(self, x):
        lo, hi = Decimal(0), self.pi
        while True:
            mid = (lo + hi) / 2
            if mid == lo or mid == hi:
                break
            if self.cos(mid) < x:
                hi = mid
            else:
                lo = mid
        return lo

    def asin(self, x):
        lb, ub = -self.pi / 2, self.pi / 2
        while True:
            mid = (lo + hi) / 2
            if mid == lo or mid == hi:
                break
            if self.sin(mid) < x:
                lo = mid
            else:
                hi = mid
        return lo

T = Trigonometry(100)

x1, y1, r1 = map(Decimal, input().split())
x2, y2, r2 = map(Decimal, input().split())

d = ((x1 - x2)**2 + (y1 - y2)**2).sqrt()

if r1 + r2 <= d:
    s = 0

elif abs(r1 - r2) < d < r1 + r2:

    cos_ph1 = (d**2 + r1**2 - r2**2) / (2 * d * r1)
    cos_ph2 = (d**2 + r2**2 - r1**2) / (2 * d * r2)
    ph1 = T.acos(cos_ph1)
    ph2 = T.acos(cos_ph2)
    a = r1**2 * ph1 + r2**2 * ph2
    b = 4 * (d**2) * (r1**2) - (d**2 + r1**2 - r2**2)**2
    s = (4 * (a**2) - b) / (4 * a + 2 * (b.sqrt()))

else:
    s = min(r1**2 * T.pi, r2**2 * T.pi)

print(s)