cdoj 邱老师看电影

//第一次写概率dp

//写成记忆化搜索的形式比递推要更方便易懂

//不过好像还是可以写成递推的形式的 但是比较那个……

 #include<cstdio>
 #include<iostream>
 #include<cmath>
 #include<algorithm>
 #include<cstring>
 #include<cstdlib>
 #include<queue>
 #include<vector>
 #include<map>
 #include<stack>
 #include<string>

 using namespace std;

 int w,b;
 double f[][];

 double dfs(int w,int b){
     if (w==) return ;
     if (b==) return ;
     if (f[w][b]>=) return f[w][b];
     f[w][b]=(double)w/(double)(w+b);
     if (w+b>=){
             double tmp=((double)(b)/double(w+b))*((double)(b-)/(double)(w+b-));
             if (b>=) f[w][b]=f[w][b]+(tmp*((double)(b-)/(double)(w+b-))*dfs(w,b-));
             if (w>=) f[w][b]=f[w][b]+(tmp*((double)(w)/(double)(w+b-))*dfs(w-,b-));
     }
     return f[w][b];
 }

 int main(){
     scanf("%d%d",&w,&b);
     for (int i=;i<=w;i++){
             for (int j=;j<=b;j++){
                     f[i][j]=-;
             }
     }
     printf("%.9lf\n",dfs(w,b));
     return ;
 }
 /*
 1 3
 */