Problem: The dragon and the princess are arguing about what to do on the New Year's Eve. The dragon suggests flying to the mountains to watch fairies dancing in the moonlight, while the princess thinks they should just go to bed early. They are desperate to come to an amicable agreement, so they decide to leave this up to chance.

They take turns drawing a mouse from a bag which initially contains w white and b black mice. The person who is the first to draw a white mouse wins. After each mouse drawn by the dragon the rest of mice in the bag panic, and one of them jumps out of the bag itself (the princess draws her mice carefully and doesn't scare other mice). Princess draws first. What is the probability of the princess winning?

If there are no more mice in the bag and nobody has drawn a white mouse, the dragon wins. Mice which jump out of the bag themselves are not considered to be drawn (do not define the winner). Once a mouse has left the bag, it never returns to it. Every mouse is drawn from the bag with the same probability as every other one, and every mouse jumps out of the bag with the same probability as every other one.

Input

The only line of input data contains two integers w and b (0 ≤ w, b ≤ 1000).

Output

Output the probability of the princess winning. The answer is considered to be correct if its absolute or relative error does not exceed 10 - 9.

Examples

Input

1 3


Output

0.500000000


Input

5 5


Output

0.658730159

Note

Let's go through the first sample. The probability of the princess drawing a white mouse on her first turn and winning right away is 1/4. The probability of the dragon drawing a black mouse and not winning on his first turn is 3/4 * 2/3 = 1/2. After this there are two mice left in the bag — one black and one white; one of them jumps out, and the other is drawn by the princess on her second turn. If the princess' mouse is white, she wins (probability is 1/2 * 1/2 = 1/4), otherwise nobody gets the white mouse, so according to the rule the dragon wins.

Solution (in JAVA):

Solution:
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.InputMismatchException;

/**
 * http://codeforces.com/contest/148/problem/D
 * 
 * @author sultan.of.swing
 *
 */
public class TaskD {

	public FasterScanner mFScanner;
	public PrintWriter mOut;
	private int N;
	private double mProb[];
	private double mMem[][][];
	private double mMem2[][];

	public TaskD() {
		mFScanner = new FasterScanner();
		mOut = new PrintWriter(System.out);
	}

	public void solve() {
		double res;
		int white, black;

		white = mFScanner.nextInt();
		black = mFScanner.nextInt();

		if (white == 0) {
			mOut.println(0);
			return;
		} else if (black == 0) {
			mOut.println(1);
			return;
		}

		mMem = new double[white + 1][black + 1][2];

		for (int i = 0; i <= white; i++)
			for (int j = 0; j <= black; j++)
				Arrays.fill(mMem[i][j], -1);

		res = white * 1. / (white + black);
		res += black * rec(false, white, black - 1) / (white + black);

		mOut.println(res);

//		res = rec(white, black);
//		mOut.println(res);

	}

	public double rec(boolean turn, int white, int black) {

		double res = 0;
		double prob;

		if (white <= 0) {
			return 0;
		} else if (black <= 0) {
			if (turn)
				return 1;
			return 0;
		}

		if (mMem[white][black][turn ? 1 : 0] >= 0)
			return mMem[white][black][turn ? 1 : 0];

		if (turn) {
			// Princess's turn
			prob = white * 1.0 / (white + black) * (white - 1.)
					/ (white + black - 1.);
			prob += black * 1.0 / (white + black) * white
					/ (white + black - 1.);
			res = black * 1.0 / (white + black) * (black - 1.)
					/ (white + black - 1.) * rec(!turn, white, black - 2)
					+ white * 1.0 / (white + black) * black
					/ (white + black - 1.) * rec(!turn, white - 1, black - 1);
			res += prob;
		} else {
			// Dragon's turn
			prob = 1.0 * black / (white + black);
			prob *= rec(!turn, white, black - 1);
			res = prob;
		}

		return mMem[white][black][turn ? 1 : 0] = res;
	}

	public double rec(int white, int black) {

		if (white <= 0)
			return 0;
		if (black <= 0)
			return 1;

		double res;
		double res1;
		double res2;

		res1 = 1.0 * white / (white + black);
		res2 = 1.0 * black / (white + black);

		black--;
		res2 *= black * 1. / (white + black);
		black--;

		if (res2 > 0) {
			double pBlack = black * 1.0 / (white + black)
					* rec(white, black - 1);
			double pWhite = white * 1.0 / (white + black)
					* rec(white - 1, black);
			res2 *= (pBlack + pWhite);
		}

		res = res1 + res2;
		return res;

	}

	void flush() {
		mOut.flush();
	}

	public void close() {
		mOut.close();
	}

	public static void main(String[] args) {
		TaskD mSol = new TaskD();
		mSol.solve();
		mSol.flush();
		mSol.close();
	}

	class FasterScanner {
		private InputStream mIs;
		private byte[] buf = new byte[1024];
		private int curChar;
		private int numChars;

		public FasterScanner() {
			this(System.in);
		}

		public FasterScanner(InputStream is) {
			mIs = is;
		}

		public int read() {
			if (numChars == -1)
				throw new InputMismatchException();
			if (curChar >= numChars) {
				curChar = 0;
				try {
					numChars = mIs.read(buf);
				} catch (IOException e) {
					throw new InputMismatchException();
				}
				if (numChars <= 0)
					return -1;
			}
			return buf[curChar++];
		}

		public String nextLine() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isEndOfLine(c));
			return res.toString();
		}

		public String nextString() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			StringBuilder res = new StringBuilder();
			do {
				res.appendCodePoint(c);
				c = read();
			} while (!isSpaceChar(c));
			return res.toString();
		}

		public long nextLong() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			long res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

		public int nextInt() {
			int c = read();
			while (isSpaceChar(c))
				c = read();
			int sgn = 1;
			if (c == '-') {
				sgn = -1;
				c = read();
			}
			int res = 0;
			do {
				if (c < '0' || c > '9')
					throw new InputMismatchException();
				res *= 10;
				res += c - '0';
				c = read();
			} while (!isSpaceChar(c));
			return res * sgn;
		}

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

		public boolean isSpaceChar(int c) {
			return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
		}

		public boolean isEndOfLine(int c) {
			return c == '\n' || c == '\r' || c == -1;
		}

		public char[] nextCharArray(int N) {
			int i;
			char[] array;
			String str;

			array = new char[N];

			i = 0;

			str = nextLine();

			for (i = 0; i < N && i < str.length(); i++) {
				array[i] = str.charAt(i);
			}

			return array;
		}

		public char[][] nextChar2DArray(int M, int N) {
			int i;
			char[][] array;

			array = new char[M][N];

			i = 0;

			for (i = 0; i < M; i++) {
				array[i] = nextCharArray(N);
			}

			return array;
		}

		public int[] nextIntArray(int N) {
			int i;
			int[] array;

			array = new int[N];

			i = 0;

			for (i = 0; i < N; i++) {
				array[i] = nextInt();
			}

			return array;
		}

		public int[][] nextInt2DArray(int M, int N) {
			int i;
			int[][] array;

			array = new int[M][N];

			i = 0;

			for (i = 0; i < M; i++) {
				array[i] = nextIntArray(N);
			}

			return array;
		}

		public long[] nextLongArray(int N) {
			int i;
			long[] array;

			array = new long[N];

			i = 0;

			for (i = 0; i < N; i++) {
				array[i] = nextLong();
			}

			return array;
		}

		public long[][] nextLong2DArray(int M, int N) {
			int i;
			long[][] array;

			array = new long[M][N];

			i = 0;

			for (i = 0; i < M; i++) {
				array[i] = nextLongArray(N);
			}

			return array;
		}

		public double[] nextDoubleArray(int N) {
			int i;
			double[] array;

			array = new double[N];

			for (i = 0; i < N; i++) {
				array[i] = nextDouble();
			}

			return array;
		}

		public double[][] nextDouble2DArray(int M, int N) {
			int i;
			double[][] array;

			array = new double[M][N];

			for (i = 0; i < M; i++) {
				array[i] = nextDoubleArray(N);
			}

			return array;
		}

	}
}