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.BufferedReader;
import java.io.FileReader;
import java.io.IOException; 
import java.io.InputStreamReader; 
import java.util.Scanner; 
import java.util.StringTokenizer; 
import java.util.*;
import java.io.*;
public class codeforces 
{ 
   static class Student{
       int x,y;//z;
        Student(int x,int y){
            this.x=x;
            this.y=y;
            //this.z=z;
        }
    }
    static int prime[];
    static void sieveOfEratosthenes(int n) 
    { 
        // Create a boolean array "prime[0..n]" and initialize 
        // all entries it as true. A value in prime[i] will 
        // finally be false if i is Not a prime, else true. 
        int pos=0;
        prime= new int[n+1]; 
        for(int p = 2; p*p <=n; p++) 
        { 
            // If prime[p] is not changed, then it is a prime 
            if(prime[p] == 0)
            { 
                // Update all multiples of p
                prime[p]=p;
                for(int i = p*p; i <= n; i += p)
                    if(prime[i]==0)
                    prime[i] = p; 
            } 
        } 
    }
static    class Sortbyroll implements Comparator<Student> 
{ 
    // Used for sorting in ascending order of 
    // roll number 
    public int compare(Student c, Student b) 
    {
        if(c.x<b.x)
            return c.x-b.x;
        if(b.x<c.x)
            return 1;
        return c.y - b.y;
    } 
} 
static class FastReader 
    { 
        BufferedReader br; 
        StringTokenizer st; 
  
        public FastReader() 
        { 
            br = new BufferedReader(new
                     InputStreamReader(System.in)); 
        } 
  
        String next() 
        { 
            while (st == null || !st.hasMoreElements()) 
            { 
                try
                { 
                    st = new StringTokenizer(br.readLine()); 
                } 
                catch (IOException  e) 
                { 
                    e.printStackTrace(); 
                } 
            } 
            return st.nextToken(); 
        } 
  
        int nextInt() 
        { 
            return Integer.parseInt(next()); 
        } 
  
        long nextLong() 
        { 
            return Long.parseLong(next()); 
        } 
  
        double nextDouble() 
        { 
            return Double.parseDouble(next()); 
        } 
  
        String nextLine() 
        { 
            String str = ""; 
            try
            { 
                str = br.readLine(); 
            } 
            catch (IOException e) 
            { 
                e.printStackTrace(); 
            } 
            return str; 
        } 
    } 
 
    static class Edge{
        int a,b;
        Edge(int a,int b){
            this.a=a;
            this.b=b;
        }
    }
    static class Trie{
        HashMap<Character,Trie>map;
         int c;
        Trie(){
            map=new HashMap<>();
            //z=null;
            //o=null;
            c=0;
        }
    }
    //static long ans;
    static int parent[];
    static int rank[];
   // static int b[][];
    static int bo[][];
    static int ho[][];
    static int seg[];
    //static int pos;
    static long mod=1000000000+7;
    //static int dp[][];
    static HashMap<String,Integer>map;
    static PriorityQueue<Student>q=new PriorityQueue<>();
    //static Stack<Integer>st;
   // static ArrayList<Character>ans;
    static ArrayList<ArrayList<Integer>>adj;
    //static long ans;
    static int pos;
    static Trie root;
    static long fac[];
    static int gw,gb;
    //static long mod=(long)(998244353);
    static long ans;
    static void solve()throws IOException{
        FastReader sc=new FastReader();
        int w,b,i,j;
        w=sc.nextInt();
        b=sc.nextInt();
        double dp[][]=new double[w+1][b+1];
        for(i=0;i<=w;i++){
            for(j=0;j<=b;j++){
                dp[i][j]=-1.0;
            }
        }
        tr(w,b,dp);
        System.out.println(tr(w,b,dp));
    }
    static double tr(int w,int b,double dp[][]){
        if(w<=0){
            //dp[w][b]=0.0;
            return 0.0;
        }
        if(b<=0){
            //dp[w][b]=1.0;
            return 1.0;
        }
        if(dp[w][b]!=-1.0)
            return dp[w][b];
        if(b<2){
            double ans=((double)w/(double)(w+b));
            dp[w][b]=ans;
            return ans;
        }
        double ans=(double)w/(double)(w+b)+((double)b/(double)(w+b))*((double)(b-1)/(double)(w+b-1))*(((double)w/(double)(w+b-2))*tr(w-1,b-2,dp)+((double)(b-2)/(double)(w+b-2))*tr(w,b-3,dp));
        dp[w][b]=ans;
        return dp[w][b];
    }
    static void update(int s,int e,int l,int r,int i,int seg[][],int lazy[][],int in){
        if(lazy[i][in]!=0){
            seg[i][in]+=1;
            if(s!=e){
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            lazy[i][in]=0;
        }
        if(s>r||l>e||s>e)
            return;
        if(l<=s&&e<=r){
            seg[i][in]+=1;
            if(s!=e){
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            return;
        }
        int mid=(s+e)/2;
        update(s,mid,l,r,i,seg,lazy,2*in+1);
        update(mid+1,e,l,r,i,seg,lazy,2*in+2);
        seg[i][in]=seg[i][2*in+1]+seg[i][2*in+2];
    }
       static int query(int s,int e,int l,int r,int i,int seg[][],int lazy[][],int in){
        if(lazy[i][in]!=0){
            seg[i][in]+=1;
            if(s!=e){
                //System.out.println(s+" "+e+" "+in);
                lazy[i][2*in+1]=1;
                lazy[i][2*in+2]=1;
            }
            lazy[i][in]=0;
        }
        if(s>r||l>e||s>e)
            return Integer.MAX_VALUE;
        if(s>=l&&e<=r){
            return seg[i][in];
        }
        int mid=(s+e)/2;
        return Math.min(query(s,mid,l,r,i,seg,lazy,2*in+1),
        query(mid+1,e,l,r,i,seg,lazy,2*in+2));
        //seg[in]=seg[2*in+1]+seg[2*in+2];
    }
    static boolean isSafe(int x,int y,int b[][],String s[] ){
        if(x>=0&&x<b.length&&y>=0&&y<b[0].length&&s[x].charAt(y)=='#'&&b[x][y]==0)
            return true;
        return false;
    }
    static void add(int x,int y,Queue<Integer>q,Queue<Integer>v,int b[][]){
        q.add(x);
        v.add(y);
        b[x][y]=1;
    }
    static long nCr(long n, long r, 
                                    long p) 
    { 
        return (fac[(int)n]* modInverse(fac[(int)r], p) 
                % p * modInverse(fac[(int)(n-r)], p) 
                                    % p) % p; 
    } 
    //static int prime[];
    //static int dp[];
    public static void main(String[] args){
        //long sum=0;
        try {
                codeforces.solve();
                } catch (Exception e) {
                    e.printStackTrace();
                }
    }
       static long modInverse(long n, long p) 
    { 
        return power(n, p-(long)2,p); 
    } 
 static long power(long x, long y, long p) 
{ 
    long res = 1;      // Initialize result 
  
    x = x % p;  // Update x if it is more than or  
                // equal to p 
  
    while (y > 0) 
    { 
        // If y is odd, multiply x with result 
        if (y %(long)2!=0) 
            res = (res*x) % p; 
  
        // y must be even now 
        y = y>>1; // y = y/2 
        x = (x*x) % p;   
    } 
    return res%p;
 }
    /*public static long power(long x,long a) {
		if(a==0) return 1;
		if(a%2==1)return (x*1L*power(x,a-1))%mod;
		return (power((int)((x*1L*x)%mod),a/2))%mod;
	}*/
   static int find(int x) 
    { 
        // Finds the representative of the set 
        // that x is an element of 
        while(parent[x]!=x) 
        { 
            // if x is not the parent of itself 
            // Then x is not the representative of 
            // his set,
            x=parent[x];
  
            // so we recursively call Find on its parent 
            // and move i's node directly under the 
            // representative of this set 
        } 
  
        return x; 
    }
    static void union(int x, int y) 
    { 
        // Find representatives of two sets 
        int xRoot = find(x), yRoot = find(y); 
  
        // Elements are in the same set, no need 
        // to unite anything. 
        if (xRoot == yRoot) 
            return; 
  
         // If x's rank is less than y's rank 
        if (rank[xRoot] < rank[yRoot]) 
  
            // Then move x under y  so that depth 
            // of tree remains less 
            parent[xRoot] = yRoot; 
  
        // Else if y's rank is less than x's rank 
        else if (rank[yRoot] < rank[xRoot]) 
  
            // Then move y under x so that depth of 
            // tree remains less 
            parent[yRoot] = xRoot; 
  
        else // if ranks are the same 
        { 
            // Then move y under x (doesn't matter 
            // which one goes where) 
            parent[yRoot] = xRoot; 
  
            // And increment the the result tree's 
            // rank by 1 
            rank[xRoot] = rank[xRoot] + 1; 
        } 
    } 
    static long gcd(long a, long b) 
    { 
        if (a == 0){ 
             //ans+=b;
            return b;
        }
        return gcd(b % a, a); 
    }
}