#include <iostream>
#include <random>
#include <iomanip>

int main(){
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    
    std::random_device seed_gen;
    std::mt19937 engine(seed_gen());
    int n, k;
    std::cin >> n >> k;
    int scoreTaro = 0;
    int scoreJiro = 0;
    int winTaro = 0;
    const int battleNum = 10000000;
    for(int i=0; i<battleNum; ++i){
        scoreTaro = scoreJiro = 0;
        for(int j=0; j<n-k; ++j){
            scoreTaro += engine()%6+1;
        }
        for(int j=0; j<k; ++j){
            scoreTaro += engine()%3+4;
        }
        for(int j=0; j<n; ++j){
            scoreJiro += engine()%6+1;
        }
        if(scoreTaro > scoreJiro){
            ++winTaro;
        }
    }
    std::cout << std::fixed << std::setprecision(6) << winTaro*1.0/battleNum << "\n";

    return 0;
}