/* -*- coding: utf-8 -*-
 *
 * 1268.cc:  No.1268 Fruit Rush 2 - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

ll as[MAX_N];
int dp[MAX_N];

/* subroutines */

inline void setmax(int &a, int b) { if (a < b) a = b; }

/* main */

int main() {
  int n;
  scanf("%d", &n);

  for (int i = 0; i < n; i++) scanf("%lld", as + i);
  sort(as, as + n);

  for (int i = n - 1; i >= 0; i--) {
    dp[i] = 1;
    if (i + 1 < n && as[i + 1] == as[i] + 2) setmax(dp[i], dp[i + 1] + 1);
    if (i + 2 < n && as[i + 2] == as[i] + 2) setmax(dp[i], dp[i + 2] + 1);
  }
  //for (int i = 0; i < n; i++) printf("%d ", dp[i]); putchar('\n');

  ll sum = 0;
  for (int i = 0; i < n; i++) {
    sum++;
    if (i + 1 < n && as[i + 1] == as[i] + 1) {
      sum++;
      if (i + 2 < n && as[i + 2] == as[i] + 3) sum += dp[i + 2];
      if (i + 3 < n && as[i + 3] == as[i] + 3) sum += dp[i + 3];
    }
  }

  printf("%lld\n", sum);
  return 0;
}