#include <iostream>
#include <vector>
#include <string>
#include <cstring>
#include <math.h>
#include <cmath>
#include <limits.h>
#include <map>
#include <set>
#include <queue>
#include <algorithm>
#include <functional>
#include <stdio.h>
#include <random>
using namespace std;

long long MOD = 1000000007;

int main() {
    
    int N,K;
    cin >> N >> K;
    
    random_device seed_gen;
    mt19937 engine(seed_gen());
    
    uniform_real_distribution<> dist(0, 1.0);
    
    long long win = 0;
    for ( long long n = 0; n < 1000000; n++ ) {
      
        int T = 0;
        int J = 0;
        for ( int i = 0; i < N; i++ ) {
            J += floor( dist(engine)*6 ) + 1;
        }
        
        for ( int i = 0; i < N-K; i++ ) {
            T += floor( dist(engine)*6 ) + 1;
        }
        for ( int i = 0; i < K; i++ ) {
            T += floor( dist(engine)*3 ) + 4;
        }
        
        if ( T > J ) { win++; }
    }
    
    printf( "%f", static_cast<double>(win) / 1000000.0 ); 
    
    return 0;
}