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
import sys
import math
from decimal import *
pi = Decimal('3.141592653589793238462643383279502884197169399375105820974')

def cos(x):
	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
	getcontext().prec -= 2
	return +s
 
def sin(x):
	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
	getcontext().prec -= 2
	return +s
 
def acos(x):
	getcontext().prec += 2
	y, y0, b = Decimal(0.0), Decimal(0), Decimal(0.5) * Decimal(math.pi)
	if x < Decimal(-1.0) or x > Decimal(1.0): 
		return Decimal(0.0)
	for i in range(80):
	    y0 = y
	    y += b
	    if cos(y) < x:
	    	y = y0
	    b *= Decimal(0.5)
	getcontext().prec -= 2
	return y
 
x1, y1, r1 = [Decimal(x) for x in sys.stdin.readline().strip().split(" ")]
x2, y2, r2 = [Decimal(x) for x in sys.stdin.readline().strip().split(" ")]
 
d = ((x2 - x1) ** 2 + (y2 - y1) ** 2).sqrt()
 
if d >= r1 + r2:
	print(0.0)
elif d <= max(r2 - r1, r1 - r2):
	print(Decimal(math.pi) * min(r1, r2) ** 2)
else:
	# f1 = 2 * acos((r1 ** 2 - r2 ** 2 + d ** 2) / (2 * r1 * d))
	# f2 = 2 * acos((r2 ** 2 - r1 ** 2 + d ** 2) / (2 * r2 * d))
 
	# s1 = r1 ** 2 * (f1 - sin(f1)) / 2
	# s2 = r2 ** 2 * (f2 - sin(f2)) / 2
	# print(s1 + s2)

	# wrong answer1
	angle1 = acos((r1 ** 2 - r2 ** 2 + d ** 2) / (2 * r1 * d))
	angle2 = acos((r2 ** 2 - r1 ** 2 + d ** 2) / (2 * r2 * d))
	tri1 = r1**2 * cos(angle1) * sin(angle1)
	tri2 = r2**2 * cos(angle2) * sin(angle2)  
	print(r1**2 * angle1 - tri1 + r2**2 * angle2 - tri2)
	
	# wrong answer2
	# f1 = acos((r1 ** 2 - r2 ** 2 + d ** 2) / (2 * r1 * d))
	# f2 = acos((r2 ** 2 - r1 ** 2 + d ** 2) / (2 * r2 * d))
	# # s = r1**2 * f1 + r2**2 * f2 - ((-d+r1+r2)*(d+r1-r2)*(d-r1+r2)*(d+r1+r2)).sqrt() / 2
	# print(s)


	# Wrong Answer3
	# a = (d**2 + r1**2 - r2**2) / 2
	# df = (d**2 * r1**2 - a**2).sqrt()
	# ix1, ix2 = (a*dx + dy*df) / (d**2), (a*dx - dy*df) / (d**2)
	# iy1, iy2 = (a*dy - dx*df) / (d**2), (a*dy + dx*df) / (d**2)

	# ix1 += x1
	# ix2 += x1
	# iy1 += y1
	# iy2 += y1

	# cx = (ix1 + ix2) / 2
	# cy = (iy1 + iy2) / 2

	# if isinstance(cx, complex) or isinstance(cy, complex):
	#     print(0)
	#     exit()

	# angle1 = acos(((cx-x1)**2 + (cy-y1)**2).sqrt() / r1)
	# angle2 = acos(((cx-x2)**2 + (cy-y2)**2).sqrt() / r2)
	# s = r1**2 * angle1 + r2**2 * angle2 - d*r1*sin(angle1)
	# print(s)