Problem: Kleofáš is participating in an n-thlon - a tournament consisting of n different competitions in n different disciplines (numbered 1 through n). There are m participants in the n-thlon and each of them participates in all competitions.

In each of these n competitions, the participants are given ranks from 1 to m in such a way that no two participants are given the same rank - in other words, the ranks in each competition form a permutation of numbers from 1 to m. The score of a participant in a competition is equal to his/her rank in it.

The overall score of each participant is computed as the sum of that participant's scores in all competitions.

The overall rank of each participant is equal to 1 + k, where k is the number of participants with strictly smaller overall score.

The n-thlon is over now, but the results haven't been published yet. Kleofáš still remembers his ranks in each particular competition; however, he doesn't remember anything about how well the other participants did. Therefore, Kleofáš would like to know his expected overall rank.

All competitors are equally good at each discipline, so all rankings (permutations of ranks of everyone except Kleofáš) in each competition are equiprobable.

Input

The first line of the input contains two space-separated integers n (1 ≤ n ≤ 100) and m (1 ≤ m ≤ 1000) — the number of competitions and the number of participants respectively.

Then, n lines follow. The i-th of them contains one integer xi (1 ≤ xi ≤ m) — the rank of Kleofáš in the i-th competition.

Output

Output a single real number – the expected overall rank of Kleofáš. Your answer will be considered correct if its relative or absolute error doesn't exceed 10 - 9.

Namely: let's assume that your answer is a, and the answer of the jury is b. The checker program will consider your answer correct, if <image>.

Examples

Input

4 10
2
1
2
1


Output

1.0000000000000000


Input

5 5
1
2
3
4
5


Output

2.7500000000000000


Input

3 6
2
4
2


Output

1.6799999999999999

Note

In the first sample, Kleofáš has overall score 6. Nobody else can have overall score less than 6 (but it's possible for one other person to have overall score 6 as well), so his overall rank must be 1.

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")
using namespace std;
const double inf = 1e121;
const double eps = 1e-10;
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
long long randint(long long l, long long r) {
  long long out = rng() % (r - l + 1) + l;
  return out >= l ? out : out + r - l + 1;
}
template <typename A, typename B>
string to_string(pair<A, B> p);
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p);
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p);
string to_string(const string& s) { return '"' + s + '"'; }
string to_string(const char* s) { return to_string((string)s); }
string to_string(bool b) { return (b ? "true" : "false"); }
string to_string(vector<bool> v) {
  bool first = true;
  string res = "{";
  for (long long i = 0; i < static_cast<long long>(v.size()); i++) {
    if (!first) {
      res += ",";
    }
    first = false;
    res += to_string(v[i]);
  }
  res += "}";
  return res;
}
template <size_t N>
string to_string(bitset<N> v) {
  string res = "";
  for (size_t i = 0; i < N; i++) {
    res += static_cast<char>('0' + v[i]);
  }
  return res;
}
template <typename A>
string to_string(A v) {
  bool first = true;
  string res = "{";
  for (const auto& x : v) {
    if (!first) {
      res += ",";
    }
    first = false;
    res += to_string(x);
  }
  res += "}";
  return res;
}
template <typename A, typename B>
string to_string(pair<A, B> p) {
  return "(" + to_string(p.first) + "," + to_string(p.second) + ")";
}
template <typename A, typename B, typename C>
string to_string(tuple<A, B, C> p) {
  return "(" + to_string(get<0>(p)) + "," + to_string(get<1>(p)) + "," +
         to_string(get<2>(p)) + ")";
}
template <typename A, typename B, typename C, typename D>
string to_string(tuple<A, B, C, D> p) {
  return "(" + to_string(get<0>(p)) + "," + to_string(get<1>(p)) + "," +
         to_string(get<2>(p)) + "," + to_string(get<3>(p)) + ")";
}
template <typename A, typename B, typename C, typename D, typename E>
string to_string(tuple<A, B, C, D, E> p) {
  return "(" + to_string(get<0>(p)) + "," + to_string(get<1>(p)) + "," +
         to_string(get<2>(p)) + "," + to_string(get<3>(p)) + "," +
         to_string(get<4>(p)) + ")";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << to_string(H);
  debug_out(T...);
}
const long long INF = 0x3f3f3f3f3f3f3f3fll;
template <typename T>
typename enable_if<!is_integral<T>::value, void>::type read(T& x) {
  cin >> x;
}
long long read() {
  char c;
  long long out = 0, f = 1;
  for (c = getchar(); !isdigit(c) && c != '-'; c = getchar())
    ;
  if (c == '-') {
    f = -1;
    c = getchar();
  }
  for (; isdigit(c); c = getchar()) out = (out << 3) + (out << 1) + c - '0';
  return out * f;
}
template <typename T>
typename enable_if<is_integral<T>::value, T>::type read(T& x) {
  char c;
  T f = 1;
  x = 0;
  for (c = getchar(); !isdigit(c) && c != '-'; c = getchar())
    ;
  if (c == '-') {
    f = -1;
    c = getchar();
  }
  for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0';
  return x *= f;
}
char read(char& x) {
  for (x = getchar(); isspace(x); x = getchar())
    ;
  return x;
}
double read(double& x) {
  scanf("%lf", &x);
  return x;
}
long double read(long double& x) {
  scanf("%Lf", &x);
  return x;
}
template <typename T>
typename enable_if<!is_integral<T>::value, void>::type write(const T& x) {
  cout << x;
}
template <typename T>
typename enable_if<is_integral<T>::value, void>::type write(const T& x) {
  if (x < 0) {
    putchar('-');
    write(-x);
    return;
  }
  if (x > 9) write(x / 10);
  putchar(x % 10 + '0');
}
void write(const char& x) { putchar(x); }
void write(const double& x) { printf("%.10lf", x); }
void write(const long double& x) { printf("%.10Lf", x); }
template <typename T, typename... Args>
void read(T& x, Args&... args) {
  read(x);
  read(args...);
}
template <
    typename OutputIt,
    typename = typename enable_if<
        is_same<output_iterator_tag,
                typename iterator_traits<OutputIt>::iterator_category>::value ||
        (is_base_of<forward_iterator_tag, typename iterator_traits<OutputIt>::
                                              iterator_category>::value &&
         !is_const<OutputIt>::value)>::type>
void read(OutputIt __first, OutputIt __last) {
  for (; __first != __last; ++__first) read(*__first);
}
template <
    typename InputIt,
    typename = typename enable_if<is_base_of<
        input_iterator_tag,
        typename iterator_traits<InputIt>::iterator_category>::value>::type>
void wts(InputIt __first, InputIt __last) {
  bool isFirst = true;
  for (; __first != __last; ++__first) {
    if (isFirst)
      isFirst = false;
    else
      putchar(' ');
    write(*__first);
  }
  putchar('\n');
}
template <
    typename InputIt,
    typename = typename enable_if<is_base_of<
        input_iterator_tag,
        typename iterator_traits<InputIt>::iterator_category>::value>::type>
void wtb(InputIt __first, InputIt __last) {
  for (; __first != __last; ++__first) {
    write(*__first);
    putchar('\n');
  }
}
template <typename T>
void wts(const T& x) {
  write(x);
  putchar(' ');
}
template <typename T>
void wtb(const T& x) {
  write(x);
  putchar('\n');
}
template <typename T>
void wte(const T& x) {
  write(x);
  exit(0);
}
template <typename T, typename... Args>
void wts(const T& x, Args... args) {
  wts(x);
  wts(args...);
}
template <typename T, typename... Args>
void wtb(const T& x, Args... args) {
  wts(x);
  wtb(args...);
}
template <typename T, typename... Args>
void wte(const T& x, Args... args) {
  wts(x);
  wte(args...);
}
template <typename T>
inline bool up(T& x, const T& y) {
  return x < y ? x = y, 1 : 0;
}
template <typename T>
inline bool dn(T& x, const T& y) {
  return y < x ? x = y, 1 : 0;
}
template <typename T>
inline bool inRange(const T& x, const T& l, const T& r) {
  return !(x < l) && !(r < x);
}
template <typename valueType, typename tagType>
class segmentTreeNode {
 public:
  long long id, left, right;
  valueType val;
  tagType tag;
};
template <typename valueType, typename tagType,
          valueType (*merge)(valueType, valueType),
          void (*update)(segmentTreeNode<valueType, tagType>&, tagType)>
class segmentTree {
 private:
  std::vector<segmentTreeNode<valueType, tagType>> nodes;
  long long leftRange, rightRange;
  valueType valueZero;
  tagType tagZero;
  void pushup(long long cur) {
    nodes[cur].val = merge(nodes[cur << 1].val, nodes[cur << 1 | 1].val);
  }
  void pushdown(long long cur) {
    update(nodes[cur << 1], nodes[cur].tag);
    update(nodes[cur << 1 | 1], nodes[cur].tag);
    nodes[cur].tag = tagZero;
  }
  void build(long long cur, long long l, long long r,
             const std::vector<valueType>& initValue) {
    nodes[cur].id = cur;
    nodes[cur].left = l;
    nodes[cur].right = r;
    nodes[cur].tag = tagZero;
    if (l == r - 1)
      nodes[cur].val = initValue[l - leftRange];
    else {
      build(cur << 1, l, (l + r) >> 1, initValue);
      build(cur << 1 | 1, (l + r) >> 1, r, initValue);
      pushup(cur);
    }
  }
  void init(const std::vector<valueType>& _initValue,
            const valueType& _valueZero, const tagType& _tagZero) {
    valueZero = _valueZero;
    tagZero = _tagZero;
    nodes.resize((rightRange - leftRange) << 2);
    build(1, leftRange, rightRange, _initValue);
  }
  void modify(long long cur, long long l, long long r, long long L, long long R,
              const tagType& tag) {
    if (l >= R || r <= L) return;
    if (L <= l && r <= R)
      update(nodes[cur], tag);
    else {
      pushdown(cur);
      modify(cur << 1, l, (l + r) >> 1, L, R, tag);
      modify(cur << 1 | 1, (l + r) >> 1, r, L, R, tag);
      pushup(cur);
    }
  }
  valueType query(long long cur, long long l, long long r, long long L,
                  long long R) {
    if (l >= R || r <= L) return valueZero;
    if (L <= l && r <= R) return nodes[cur].val;
    pushdown(cur);
    return merge(query(cur << 1, l, (l + r) >> 1, L, R),
                 query(cur << 1 | 1, (l + r) >> 1, r, L, R));
  }

 public:
  segmentTree() {}
  segmentTree(long long _leftRange, long long _rightRange,
              const std::vector<valueType>& _initValue,
              const valueType& _valueZero, const tagType& _tagZero) {
    leftRange = _leftRange;
    rightRange = _rightRange;
    init(_initValue, _valueZero, _tagZero);
  }
  segmentTree(long long size, const std::vector<valueType>& _initValue,
              const valueType& _valueZero, const tagType& _tagZero) {
    leftRange = 1;
    rightRange = size + 1;
    init(_initValue, _valueZero, _tagZero);
  }
  void modify(long long l, long long r, const tagType& tag) {
    modify(1, leftRange, rightRange, l, r, tag);
  }
  void modify(long long p, const tagType& tag) { modify(p, p + 1, tag); }
  valueType query(long long l, long long r) {
    return query(1, leftRange, rightRange, l, r);
  }
  valueType query(long long p) { return query(p, p + 1); }
};
class maxFlow {
 private:
  std::queue<long long> q;
  std::vector<long long> head, cur, nxt, to, dep;
  std::vector<long long> cap;

 public:
  maxFlow(long long _n = 0) { init(_n); }
  void init(long long _n) {
    head.clear();
    head.resize(_n + 1, 0);
    nxt.resize(2);
    to.resize(2);
    cap.resize(2);
  }
  void init() { init(head.size() - 1); }
  void add(long long u, long long v, long long w) {
    nxt.push_back(head[u]);
    head[u] = to.size();
    to.push_back(v);
    cap.push_back(w);
  }
  void Add(long long u, long long v, long long w) {
    add(u, v, w);
    add(v, u, 0);
  }
  void del(long long x) { cap[x << 1] = cap[x << 1 | 1] = 0; }
  bool bfs(long long s, long long t) {
    dep.clear();
    dep.resize(head.size(), -1);
    dep[s] = 0;
    q.push(s);
    while (!q.empty()) {
      long long u = q.front();
      q.pop();
      for (long long i = head[u]; i; i = nxt[i]) {
        long long v = to[i];
        long long w = cap[i];
        if (w > 0 && dep[v] == -1) {
          dep[v] = dep[u] + 1;
          q.push(v);
        }
      }
    }
    return ~dep[t];
  }
  long long dfs(long long u, long long flow, long long t) {
    if (dep[u] == dep[t]) return u == t ? flow : 0;
    long long out = 0;
    for (long long& i = cur[u]; i; i = nxt[i]) {
      long long v = to[i];
      long long w = cap[i];
      if (w > 0 && dep[v] == dep[u] + 1) {
        long long f = dfs(v, std::min(w, flow - out), t);
        cap[i] -= f;
        cap[i ^ 1] += f;
        out += f;
        if (out == flow) return out;
      }
    }
    return out;
  }
  long long maxflow(long long s, long long t) {
    long long out = 0;
    while (bfs(s, t)) {
      cur = head;
      out += dfs(s, 0x7fffffffffffffffll, t);
    }
    return out;
  }
  long long getflow(long long x) const { return cap[x << 1 | 1]; }
};
struct customHash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM = rng();
    return splitmix64(x + FIXED_RANDOM);
  }
};
vector<long long> a;
long long n, m;
vector<double> f, g;
double calc(long long l, long long r) {
  if (r < 0) return 0;
  if (l <= 0) return g[r];
  return g[r] - g[l - 1];
}
signed main() {
  read(n, m);
  if (m == 1) wte(1);
  a.resize(n + 1, 0);
  read(a.begin() + 1, a.end());
  g.resize(n * m + 1, 1);
  f.resize(n * m + 1);
  for (long long i = (1), iend = (n); i <= iend; ++i) {
    for (long long j = (i), jend = (m * i); j <= jend; ++j)
      f[j] = (calc(j - m, j - 1) - calc(j - a[i], j - a[i])) / (m - 1);
    g.assign(n * m + 1, 0);
    for (long long j = (i), jend = (n * m); j <= jend; ++j)
      g[j] = g[j - 1] + f[j];
  }
  long long sum = 0;
  for (auto x : a) sum += x;
  write(calc(n, sum - 1) * (m - 1) + 1);
  return 0;
}