////  main.cpp//  uva11429////  Created by New_Life on 16/8/4.//  Copyright © 2016年 chenhuan001. All rights reserved.//#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          using namespace std;#define N 1010#define eps 1e-12long double g[N];int main(int argc, const char * argv[]) {    int r,n;    while(scanf("%d%d",&r,&n) && !(r==0&&n==0))    {        for(int i=0;i
          
           1e-10); printf("%.6Lf\n",ans); } return 0;}/* 100 3 1 3 1 3 1 3 2 4 1 4 1 4 1 4 1 4 2 3 1 3 1 3 1 3 10 2 1 2 1 2 */
          
         
        
       
      
     

//用long double 才过的...