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
//package educational.round02;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.math.BigDecimal;
import java.math.MathContext;
import java.util.Arrays;
import java.util.InputMismatchException;

public class D2B {
	InputStream is;
	PrintWriter out;
	String INPUT = "";
//	String INPUT = "0 0 1000000000 999999999 0 1";
	
	void solve()
	{
		long x1 = ni(), y1 = ni(), r1 = ni();
		long x2 = ni(), y2 = ni(), r2 = ni();
//		double d = Point2D.distance(x1, y1, x2, y2);
		out.printf("%.14f\n", areaCircleInter(r1, r2, (x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)));
	}
	
	public double areaCircleInter(long r1, long r2, long d2)
	{
		double d = Math.sqrt(d2);
		if(d == 0)return Math.PI*Math.min(r1,r2)*Math.min(r1,r2);
		if(d >= r1 + r2){
			return 0;
		}else if(d >= Math.abs(r1-r2)){
			BigDecimal bd = sqrt(d2);
			double o1 = f(r1*r1+d2-r2*r2, 2*r1, d, bd);
			double o2 = f(r2*r2+d2-r1*r1, 2*r2, d, bd);
			return 
					o1*r1*r1 +
					o2*r2*r2;
//			return t1*r1*r1+t2*r2*r2-r1*r1/2*Math.sin(2*t1)-r2*r2/2*Math.sin(2*t2);
		}else{
			double r = Math.min(r1, r2);
			return Math.PI*r*r;
		}
	}
	
	BigDecimal sqrt(long x)
	{
		BigDecimal X = BigDecimal.valueOf(x);
		BigDecimal S = X;
		MathContext mc = new MathContext(100);
		for(int rep = 0;rep < 100;rep++){
			S = S.subtract(S.multiply(S, mc).subtract(X).divide(BigDecimal.valueOf(2).multiply(S), mc));
		}
		return S;
	}
	
	double f(long num, long den, double d, BigDecimal bd)
	{
		double eps = 1E-6;
		if(1-(double)num/den/d < eps){
			MathContext mc = new MathContext(100);
			double val = BigDecimal.ONE.subtract(BigDecimal.valueOf(num).divide(BigDecimal.valueOf(den), mc).divide(bd, mc)).doubleValue();
			double ret = 0;
//			ret -= 3*Math.pow(num/den, 3.5)/64/Math.sqrt(2);
//			ret -= 5*Math.pow(num/den, 3.5)/448/Math.sqrt(2);
			ret += Math.sqrt(2)*Math.pow(val, 2.5)/5;
			ret += 4./3*Math.sqrt(2)*Math.pow(val, 1.5);
//			tr(num, den);
			return ret;
		}else{
			double u = (double)num/den/d;
			if(u < -1)u = -1;
			if(u > 1)u = 1;
			double a = Math.acos(u);
			return a-u*Math.sqrt(1-u*u);
		}
	}

	void run() throws Exception
	{
		is = oj ? System.in : new ByteArrayInputStream(INPUT.getBytes());
		out = new PrintWriter(System.out);
		
		long s = System.currentTimeMillis();
		solve();
		out.flush();
		tr(System.currentTimeMillis()-s+"ms");
	}
	
	public static void main(String[] args) throws Exception { new D2B().run(); }
	
	private byte[] inbuf = new byte[1024];
	private int lenbuf = 0, ptrbuf = 0;
	
	private int readByte()
	{
		if(lenbuf == -1)throw new InputMismatchException();
		if(ptrbuf >= lenbuf){
			ptrbuf = 0;
			try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); }
			if(lenbuf <= 0)return -1;
		}
		return inbuf[ptrbuf++];
	}
	
	private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); }
	private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; }
	
	private double nd() { return Double.parseDouble(ns()); }
	private char nc() { return (char)skip(); }
	
	private String ns()
	{
		int b = skip();
		StringBuilder sb = new StringBuilder();
		while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ')
			sb.appendCodePoint(b);
			b = readByte();
		}
		return sb.toString();
	}
	
	private char[] ns(int n)
	{
		char[] buf = new char[n];
		int b = skip(), p = 0;
		while(p < n && !(isSpaceChar(b))){
			buf[p++] = (char)b;
			b = readByte();
		}
		return n == p ? buf : Arrays.copyOf(buf, p);
	}
	
	private char[][] nm(int n, int m)
	{
		char[][] map = new char[n][];
		for(int i = 0;i < n;i++)map[i] = ns(m);
		return map;
	}
	
	private int[] na(int n)
	{
		int[] a = new int[n];
		for(int i = 0;i < n;i++)a[i] = ni();
		return a;
	}
	
	private int ni()
	{
		int num = 0, b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private long nl()
	{
		long num = 0;
		int b;
		boolean minus = false;
		while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'));
		if(b == '-'){
			minus = true;
			b = readByte();
		}
		
		while(true){
			if(b >= '0' && b <= '9'){
				num = num * 10 + (b - '0');
			}else{
				return minus ? -num : num;
			}
			b = readByte();
		}
	}
	
	private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
	private void tr(Object... o) { if(!oj)System.out.println(Arrays.deepToString(o)); }
}
