#line 1 "main.cpp"

/**
 * @title Template
 */

#include <iostream>
#include <algorithm>
#include <utility>
#include <numeric>
#include <vector>
#include <array>
#include <cassert>

#line 2 "/Users/kodamankod/Desktop/cpp_programming/Library/other/chmin_chmax.cpp"

template <class T, class U>
constexpr bool chmin(T &lhs, const U &rhs) {
  if (lhs > rhs) { lhs = rhs; return true; }
  return false;
}

template <class T, class U>
constexpr bool chmax(T &lhs, const U &rhs) {
  if (lhs < rhs) { lhs = rhs; return true; }
  return false;
}

/**
 * @title Chmin/Chmax
 */
#line 2 "/Users/kodamankod/Desktop/cpp_programming/Library/other/range.cpp"

#line 4 "/Users/kodamankod/Desktop/cpp_programming/Library/other/range.cpp"

class range {
public:
  class iterator {
  private:
    int64_t M_position;

  public:
    constexpr iterator(int64_t position) noexcept: M_position(position) { }
    constexpr void operator ++ () noexcept { ++M_position; }
    constexpr bool operator != (iterator other) const noexcept { return M_position != other.M_position; }
    constexpr int64_t operator * () const noexcept { return M_position; }
  };

  class reverse_iterator {
  private:
    int64_t M_position;
  
  public:
    constexpr reverse_iterator(int64_t position) noexcept: M_position(position) { }
    constexpr void operator ++ () noexcept { --M_position; }
    constexpr bool operator != (reverse_iterator other) const noexcept { return M_position != other.M_position; }
    constexpr int64_t operator * () const noexcept { return M_position; }
  };
  
private:
  const iterator M_first, M_last;

public:
  constexpr range(int64_t first, int64_t last) noexcept: M_first(first), M_last(std::max(first, last)) { }
  constexpr iterator begin() const noexcept { return M_first; }
  constexpr iterator end() const noexcept { return M_last; }
  constexpr reverse_iterator rbegin() const noexcept { return reverse_iterator(*M_last - 1); } 
  constexpr reverse_iterator rend() const noexcept { return reverse_iterator(*M_first - 1); } 
};

/**
 * @title Range
 */
#line 16 "main.cpp"

using i32 = std::int32_t;
using i64 = std::int64_t;
using u32 = std::uint32_t;
using u64 = std::uint64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

constexpr i32 inf32 = (i32(1) << 30) - 1;
constexpr i64 inf64 = (i64(1) << 62) - 1;

int main() {
  usize N;
  std::cin >> N;
  std::vector<u64> A(N);
  for (auto &x: A) {
    std::cin >> x;
  }
  std::sort(A.begin(), A.end());
  std::vector<std::array<u64, 3>> dp(N);
  u64 ans = 0;
  for (auto i: range(0, N)) {
    dp[i][0] += 1;
    if (i + 1 < N) {
      for (auto j: range(0, 3)) {
        if (A[i] + j + 1 == A[i + 1]) {
          dp[i + 1][1] += dp[i][j];
        }
        if (A[i] + j - 1 == A[i + 1]) {
          dp[i + 1][2] += dp[i][j];
        }
      }
    }
    if (i + 2 < N) {
      for (auto j: range(0, 3)) {
        if (A[i] + j + 1 == A[i + 2]) {
          dp[i + 2][1] += dp[i][j];
        }
        if (A[i] + j - 1 == A[i + 2]) {
          dp[i + 2][2] += dp[i][j];
        }
      }
    }
    // std::cout << A[i] << ": ";
    for (auto x: dp[i]) {
      // std::cout << x << ' ';
      ans += x;
    }
    // std::cout << '\n';
  }
  std::cout << ans << '\n';
  return 0;
}