/* -*- coding: utf-8 -*-
 *
 * 2374.cc:  No.2374 ASKT Subsequences - yukicoder
 */

#include<cstdio>
#include<algorithm>
 
using namespace std;

/* constant */

const int MAX_N = 2000;
const int MAX_A = 2000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];
ll dp1[MAX_A], dp2[MAX_A][MAX_A], dp3[MAX_A];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i), as[i]--;

  // a2=a1+k+10, a3=a1+10, a4=a1+k+11=a2+1
  
  ll dp4 = 0;
  for (int i = 0; i < n; i++) {
    int ai = as[i];

    if (ai > 0) dp4 += dp3[ai - 1];

    if (ai >= 10)
      for (int aj = 0; aj < MAX_A; aj++) dp3[aj] += dp2[ai - 10][aj];

    for (int aj = 0; aj < ai - 10; aj++) dp2[aj][ai] += dp1[aj];

    dp1[ai]++;
  }

  printf("%lld\n", dp4);
  return 0;
}