Problem: Alex enjoys performing magic tricks. He has a trick that requires a deck of n cards. He has m identical decks of n different cards each, which have been mixed together. When Alex wishes to perform the trick, he grabs n cards at random and performs the trick with those. The resulting deck looks like a normal deck, but may have duplicates of some cards.

The trick itself is performed as follows: first Alex allows you to choose a random card from the deck. You memorize the card and put it back in the deck. Then Alex shuffles the deck, and pulls out a card. If the card matches the one you memorized, the trick is successful.

You don't think Alex is a very good magician, and that he just pulls a card randomly from the deck. Determine the probability of the trick being successful if this is the case.

Input

First line of the input consists of two integers n and m (1 ≤ n, m ≤ 1000), separated by space — number of cards in each deck, and number of decks.

Output

On the only line of the output print one floating point number – probability of Alex successfully performing the trick. Relative or absolute error of your answer should not be higher than 10 - 6.

Examples

Input

2 2


Output

0.6666666666666666


Input

4 4


Output

0.4000000000000000


Input

1 2


Output

1.0000000000000000

Note

In the first sample, with probability <image> Alex will perform the trick with two cards with the same value from two different decks. In this case the trick is guaranteed to succeed.

With the remaining <image> probability he took two different cards, and the probability of pulling off the trick is <image>.

The resulting probability is <image>

Solution (in JAVA):

Solution:
import java.io.*;
import java.lang.*;
import static java.lang.Math.*;
import java.lang.reflect.*;
import java.math.BigInteger;
import static java.math.BigInteger.*;
import java.security.CodeSource;
import java.security.KeyStore;
import java.util.*;
import static java.util.Arrays.*;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.logging.Level;
import java.util.logging.Logger;

// https://netbeans.org/kb/73/java/editor-codereference_ru.html#display
public class Main {
    //<editor-fold defaultstate="collapsed" desc="Your Fold Super Code">

    private void run() {
        Locale.setDefault(Locale.US);
        boolean oj = true;
        try {
            oj = System.getProperty("MYLOCAL") == null;
        } catch (Exception e) {
        }

        if (oj) {
            sc = new FastScanner(new InputStreamReader(System.in));
            out = new PrintWriter(new OutputStreamWriter(System.out));
        } else {
            try {
                sc = new FastScanner(new FileReader("input.txt"));
                out = new PrintWriter(new FileWriter("output.txt"));
            } catch (IOException e) {
                MLE();
            }
        }
        solve();
        //if( oj )
        err.println("Time: " + (System.currentTimeMillis() - timeBegin) / 1e3);
        out.flush();
    }

    private void show(int[] arr) {
        for( int v : arr ) err.print( " " + v );
        err.println();
    }

    private boolean eq(String a, String b) {
        for( int i = 0; i < a.length(); ++i ){
            if( a.charAt(i) == '.' ) continue;
            if( b.charAt(i) == '.' ) continue;
            if( a.charAt(i) != b.charAt(i) )
                return false;
        }
        return true;
    }

    class FastScanner {

        BufferedReader br;
        StringTokenizer st;

        FastScanner(InputStreamReader reader) {
            br = new BufferedReader(reader);
            st = new StringTokenizer("");
        }

        String next() {
            while (!st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException ex) {
                    Main.MLE();
                }
            }
            return st.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

        long nextLong() {
            return Long.parseLong(next());
        }
    }

    public static void MLE() {
        int[][] arr = new int[1024 * 1024][];
        for (int i = 0; i < arr.length; i++) {
            arr[i] = new int[1024 * 1024];
        }
    }

    public static void main(String[] args) {
        new Main().run();
    }

    long timeBegin = System.currentTimeMillis();
    FastScanner sc;
    PrintWriter out;
    PrintStream err = System.err;

    // </editor-fold>
    
    
    static double[] logFact = new double[(int)1e6+1];
    static {
        logFact[0] = log(1);
        for (int i = 1; i < logFact.length; i++) {
            logFact[i] = logFact[i-1] + log(i);
        }
        System.err.println("f:" + exp(logFact[7]));
    }
    
    double logC( int m, int n ){
        return logFact[n] - logFact[m] - logFact[n-m];
    }
    
    void solve() {
        int n = sc.nextInt();
        int m = sc.nextInt();;
        double ans = 0;
        for( int cnt = 1; cnt <= min(n,m); ++cnt ){
            double cur = logC(cnt,m) + logC(n-cnt,n*m-m) - logC(n,n*m);
//            if( -50 <= cur  ){
                cur = exp(cur);
                cur = cur * cnt * cnt / n;
                ans += cur;
//            }
        }
        out.printf( "%.10f\n", ans);
    }

}