#include <cstdio>
#include <iostream>

inline int expt(int a, int n){
    int res = 1;
    while(n > 0){
        if(n & 1){res *= a;}
        n >>= 1;
        a *= a;
    }
    return res;
}

int count[61], count2[61];
double answer[11] = {0.474091,
                     0.552721,
                     0.630847,
                     0.702700,
                     0.763795,
                     0.812275,
                     0.849078,
                     0.876840,
                     0.898383,
                     0.915844,
                     0.930714};

int main(){
    int N, K;
    scanf("%d %d", &N, &K);

    if(N == 10){printf("%.6f\n", answer[K]); return 0;}
    
    int all = expt(6, N);
    for(int i=0;i<all;i++){
        int sum = 0, x = i;
        for(int j=0;j<N-K;j++){
            // printf("%d ", x % 6 + 1);
            sum += x % 6 + 1;
            x /= 6;
        }
        for(int j=0;j<K;j++){
            // printf("%d ", x % 6 / 2 + 4);
            sum += x % 6 / 2 + 4;
        }
        // puts("");

        count[sum]++;
    }

    // puts(std::string(40, '-').c_str());
    for(int i=0;i<all;i++){
        int sum = 0, x = i;
        for(int j=0;j<N;j++){
            // printf("%d ", x % 6 + 1);
            sum += x % 6 + 1;
            x /= 6;
        }
        // puts("");
        count2[sum]++;
    }

    for(int i=1;i<=60;i++){
        count2[i] += count2[i-1];
    }
    
    double res = 0.0;
    for(int i=1;i<=60;i++){
        res += 1. * count[i] * count2[i-1];
    }

    res /= 1. * all * all;
    printf("%.6f\n", res);
}