#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
using ll = long long;

ll calc(const vector<ll> &a)
{
  int n = a.size();
  int maxA = a.back();
  vector<ll> dp(maxA + 2, 0);
  vector<bool> exist(maxA + 2, 0);
  for (int i = 0; i < n; i++)
    exist[a[i]] = true;
  for (int i = 0; i < maxA + 2; i++)
  {
    dp[i] += exist[i];
    if (i >= 2 and exist[i - 1])
      dp[i] += dp[i - 2];
  }
  ll sum = 0;
  for (int i = 0; i < maxA + 2; i++)
    sum += dp[i];
  return sum;
}

int main()
{
  int n;
  cin >> n;
  vector<ll> a(n);
  for (int i = 0; i < n; i++)
  {
    cin >> a[i];
    a[i]--;
  }
  sort(begin(a), end(a));
  a.push_back(2e18);

  ll ans = 0, minus = a[0];
  vector<ll> v;
  for (int i = 0; i < n; i++)
  {
    v.push_back(a[i] - minus);
    if (a[i + 1] - a[i] >= 3)
    {
      ans += calc(v);
      v.clear();
      minus = a[i + 1];
    }
  }
  cout << ans << "\n";
  return 0;
}