package BiShi.AQY; import java.io.File; import java.io.FileNotFoundException; import java.text.DecimalFormat; import java.util.Scanner; public class AQY_2 { public static double dp(double n,double m){ if(n==0)return 0; if(m==0)return 1; if(m==1){ return n/(n+1.0); } if(m==2){ return n/(n+2.0); } double res=n/(m+n) + (m/(m+n))*((m-1)/(m+n-1))*((m-2)/(m+n-2))*dp(n,m-3); res += (m/(m+n))*(m-1)/(m+n-1)*(n/(m+n-2))*dp(n-1,m-2); return res; } public static void main(String[] args) throws FileNotFoundException { Scanner sc=new Scanner(new File("/home/mao/workspace/java/src/BiShi/AQY/test2")); //Scanner sc=new Scanner(System.in); while (sc.hasNext()){ double n=sc.nextDouble(); double m=sc.nextDouble(); double res=dp(n,m); DecimalFormat df = new DecimalFormat("#0.00000"); System.out.println(df.format(res)); } } }