#include <bits/stdc++.h>   using namespace std;   const long long int inf = 1000000000;   const long long int mod = 1000000000 + 7;   inline void IO() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);   }   inline int dcmp(long double x) { return x < -1e-12 ? -1 : (x > 1e-12); }   template <class T>   inline int CHECK(T MASK, int i) {     return (MASK >> i) & 1;   }   template <class T>   inline T ON(T MASK, int i) {     return MASK | (T(1) << i);   }   template <class T>   inline T OFF(T MASK, int i) {     return MASK & (~(T(1) << i));   }   template <typename T>   inline int CNT(T MASK) {     if (numeric_limits<T>::digits <= numeric_limits<unsigned int>::digits)       return __builtin_popcount(MASK);     else       return __builtin_popcountll(MASK);   }   template <class T>   inline int RIGHT(T MASK) {     return log2(MASK & -MASK);   }   int dx4[] = {0, 0, -1, +1};   int dy4[] = {+1, -1, 0, 0};   int dx8[] = {1, 1, 0, -1, -1, -1, 0, 1, 0};   int dy8[] = {0, 1, 1, 1, 0, -1, -1, -1, 0};   inline void I(int& a) { scanf( %d , &a); }   inline void I(long long int& a) { scanf( %I64d , &a); }   inline void I(unsigned long long int& a) { scanf( %I64u , &a); }   inline void I(char* a) { scanf( %s , a); }   char Iarr[2000010];   inline void I(string& a) {     scanf( %s , Iarr);     a = Iarr;   }   template <typename T, typename... Args>   void I(T& a, Args&... args) {     I(a);     I(args...);   }   inline void OUT(int a) { printf( %d , a); }   inline void OUT(long long int a) { printf( %I64d , a); }   inline void OUT(const char* a) { printf( %s , a); }   inline void OUT(char* a) { printf( %s , a); }   inline void OUT(bool a) { printf( %d , a); }   inline void OUT(string a) {     for (__typeof(a.end()) it = (a.begin()) - ((a.begin()) > (a.end()));          it != (a.end()) - ((a.begin()) > (a.end()));          it += 1 - 2 * ((a.begin()) > (a.end())))       printf( %c , *it);   }   inline void OUT(unsigned long long int a) { printf( %I64u , a); }   template <typename T, typename... Args>   void OUT(T a, Args... args) {     OUT(a);     OUT(   );     OUT(args...);   }   template <typename... Args>   void O(Args... args) {     OUT(args...);     OUT(  n );   }   template <typename T1, typename T2>   inline ostream& operator<<(ostream& os, pair<T1, T2> p) {     os <<  {  << p.first <<  ,   << p.second <<  } ;     return os;   }   template <typename T>   inline ostream& operator<<(ostream& os, vector<T>& a) {     os <<  [ ;     for (int i = 0; i < (int)a.size(); i++) {       if (i) os <<  ,  ;       os << a[i];     }     os <<  ] ;     return os;   }   void err(istream_iterator<string> it) {}   template <typename T, typename... Args>   void err(istream_iterator<string> it, T a, Args... args) {     cout << *it <<   =   << a << endl;     err(++it, args...);   }   const int M = 100010;   vector<pair<long long int, pair<int, int> > > ans[51];   int n, p;   long double fnl = 0;   void func() {     for (int i = 1; i <= p; i++) {       for (pair<long long int, pair<int, int> > pp : ans[i]) {         long double res = i * pp.first;         int z = 1;         int zz = 1;         int curr = 1;         while (1) {           if (res > 0) {             if (curr != n + 1)               res /= curr++;             else if (z != pp.second.first + 1)               res *= z++;             else if (zz != pp.second.second + 1)               res *= zz++;             else               break;           } else {             if (z != pp.second.first + 1)               res *= z++;             else if (zz != pp.second.second + 1)               res *= zz++;             else if (curr != n + 1)               res /= curr++;             else               break;           }         }         fnl += res;       }     }   }   int main() {     IO();     cin >> n;     int a[n];     for (int i = 0; i < n; i++) {       cin >> a[i];     }     cin >> p;     int sum = 0;     for (int i = 0; i < n; i++) {       sum += a[i];     }     if (sum <= p) {       cout << n << endl;       exit(0);     }     for (int i = 0; i < n; i++) {       vector<int> v;       for (int j = 0; j < n; j++) {         if (j != i) v.push_back(a[j]);       }       long long int dp[51][51][51] = {0};       for (int j = 0; j < n - 1; j++) {         for (int k = 0; k <= j + 1; k++) {           for (int l = 0; l <= 50; l++) {             if (j == 0) {               if (k == 1 && v[j] == l)                 dp[j][k][l] = 1;               else if (k == 0 && l == 0)                 dp[j][k][l] = 1;             } else if (k == 0) {               if (l == 0) dp[j][k][l] = 1;             } else {               dp[j][k][l] = dp[j - 1][k][l];               if (v[j] <= l) dp[j][k][l] += dp[j - 1][k - 1][l - v[j]];             }           }         }       }       for (int l = p - a[i] + 1; l <= p; l++) {         for (int gb = 1; gb <= n; gb++) {           if (l >= 0)             if ((n - 1 - gb) > 0 && (n - 2) >= 0)               ans[gb].push_back(                   make_pair(dp[n - 2][gb][l], make_pair(gb, n - 1 - gb)));             else if ((n - 1 - gb) == 0 && (n - 2) >= 0)               ans[gb].push_back(make_pair(dp[n - 2][gb][l], make_pair(gb, 1)));           int k = (int)ans[gb].size();           if (k != 0) {           }         }       }     }     func();     cout << setprecision(12) << fixed << fnl << endl;     return 0;   }