1 /**
2 对于大数的很好的应用，，缩小放大，，保持精度
3 **/
4 #include <iostream>
5 #include <cmath>
6 #include <algorithm>
7 #include <cstdio>
8 using namespace std;
9
10 int main()
11 {
12 double n,p;
13 int cnt =1;
14 while(cin>>n>>p){
15 double p1 = log(p+0.0);
16 double p2 = log(1-p+0.0);
17 double s1 = (n+1)*p1;
18 double s2 = (n+1)*p2;
19 double ans =0,c=0;
20 for(int i=0;i<n;i++){
21 ans += (exp(c+s1)+exp(c+s2))*(n-i);
22 c += log(n+1+i+0.0)-log(i+1+0.0);
23 s1 += p2;
24 s2 += p1;
25 }
26 printf("Case %d: %.6lf\n",cnt++,ans);
27 }
28 return 0;
29 }
