/* -*- coding: utf-8 -*-
 *
 * 2053.cc:  No.2053 12345... - yukicoder
 */

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

/* constant */

const int MAX_N = 200000;

/* typedef */

typedef long long ll;

/* global variables */

int as[MAX_N];

/* subroutines */

inline ll nc2(int n) { return (ll)n * (n - 1) / 2; }

/* main */

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

  ll sum = 0;
  for (int i = 0; i < n;) {
    int j = i + 1;
    while (j < n && as[j - 1] + 1 == as[j]) j++;
    sum += nc2(j - i);
    i = j;
  }

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