#include <bits/stdc++.h>
#define FOR(i,bg,ed) for(ll i=(bg);i<(ed);i++)
#define REP(i,n) FOR(i,0,n)
#define MOD 1000000007
#define int long long
using namespace std;
typedef long long ll;
const int INF = 1e9;

int N, K;
int sumCntA[65], sumCntB[65];

void dfsA(int i, int sum)
{
    if (i == N) {
        sumCntA[sum]++;
        return;
    }

    if (i < K) {
        for (int j=4; j<=6; j++) {
            REP(k,2) {
                dfsA(i + 1, sum + j);
            }
        }
    } else {
        for (int j=1; j<=6; j++) {
            dfsA(i + 1, sum + j);
        }
    }
}

void dfsB(int i, int sum)
{
    if (i == N) {
        sumCntB[sum]++;
        return;
    }

    for (int j=1; j<=6; j++) {
        dfsB(i + 1, sum + j);
    }
}

signed main()
{
    cin >> N >> K;

    REP(i,65) {
        sumCntA[i] = 0;
        sumCntB[i] = 0;
    }

    dfsA(0, 0);
    dfsB(0, 0);

    ll bunbo = pow(6, N) * pow(6, N);
    ll bunsi = 0;
    REP(i,65) REP(j,65) {
        if (i > j) {
            bunsi += sumCntA[i] * sumCntB[j];
        }
    }

    printf("%.10lf\n", 1.0 * bunsi / bunbo);
}