#define VERBOSE
    #define _USE_MATH_DEFINES
    #define _CRT_SECURE_NO_WARNINGS
    #include <algorithm>
    #include <fstream>
    #include <bitset>
    #include <cctype>
    #include <cfloat>
    #include <climits>
    #include <cmath>
    #include <cstdio>
    #include <cstdlib>
    #include <cstring>
    #include <ctime>
    #include <deque>
    #include <functional>
    #include <iomanip>
    #include <iostream>
    #include <list>
    #include <map>
    #include <numeric>
    #include <queue>
    #include <set>
    #include <sstream>
    #include <stack>
    #include <string>
    #include <vector>

    #ifndef _DEBUG
    # undef VERBOSE
    #endif
    #ifdef NDEBUG
    #define VERBOSE
    #endif

    #define eps 1e-8
    #define inf (1000 * 1000 * 1000)
    #define linf (4LL * 1000 * 1000 * 1000 * 1000 * 1000 * 1000)
    #define sqr(x) ((x) * (x))
    #define eq(x, y) (((x) > (y) ? (x) - (y) : (y) - (x)) <= eps)
    #define sz(x) int((x).size())
    #define all(x) (x).begin(), (x).end()
    #define rall(x) (x).rbegin(), (x).rend()
    #define mp make_pair
    #define FOR(i, n) for(int (i) = 0; (i) < (n); ++(i))
    #define FORN(i, n) for(int (i) = 1; (i) <= (n); ++(i))
    #define REP(i,from,to) for(int (i) = (from); (i) <= (to); ++(i))
    #define RREP(i,from,to) for(int (i) = (from); (i) >= (to); --(i))
    #define FOREACH(iter, cont) for(__typeof(cont)::iterator it = (cont).begin(); (it) != (cont).end(); ++(it))


    using namespace std;

    typedef unsigned uint;
    typedef long long llong;
    typedef unsigned long long ullong;
    typedef long double ldouble;
    typedef vector<int> vi;
    typedef vector<vi> vvi;
    typedef vector<double> vd;
    typedef vector<vd> vvd;
    struct debug_t {
      template <typename T>
      debug_t& operator<<(const T& value) {
    # ifdef VERBOSE
        cout << value;
    # endif
        return *this;
      }
    } debug;

    double dp[501][3001]; // dp[cnt][sum]
    double rec(int cnt, int sum) {
      if( sum < 0 ) return 0;
      if( dp[cnt][sum] != -1 )
        return dp[cnt][sum];
      double result = 0;
      FORN(a,6)
        result += rec(cnt-1,sum-a)/6;
      return dp[cnt][sum] = result;
    }

    int main() {
      //freopen(TASK ".in", "r", stdin);
      //freopen(TASK ".out", "w", stdout);
      freopen("input.txt", "r", stdin);
      //freopen("output.txt", "w", stdout);
      //freopen("info.txt", "r", stdin);
      //freopen("info.txt", "w", stdout);
      ios_base::sync_with_stdio(false);
      cin.tie(NULL);

      int n,q; cout << setprecision(3) << fixed;
      while( cin >> n >> q ) {
        FOR(i,501) FOR(j,3001) dp[i][j] = -1;
        FOR(j,3001) dp[1][j] = dp[0][j] = 0;
        FORN(j,6)
          dp[1][j] = 1.0 / 6.0;
        cout << rec(n,q) << "\n";
      }

      return 0;
    }