UVa Q10081

//UVa Q10081
#include <bits/stdc++.h>
using namespace std;

double dp[101][12];

int main(){
    int n,k;
    while(cin >> k >> n){
        ++k;
        memset(dp, 0, sizeof(dp));
        for(int i = 1; i <= k; ++i)dp[1][i] = 1;
        for(int i = 2; i <= n; ++i){
            for(int j = 1; j <= k; ++j){
                dp[i][j] = (dp[i-1][j-1] + dp[i-1][j] + dp[i-1][j+1]) / k;
            }
        }
        double sum = 0;
        for(int i = 1; i <= k; ++i)sum += dp[n][i];
        printf("%.5f\n", sum*100/k);
    }
    return 0;
}