#include <bits/stdc++.h>
using namespace std;
int a[200005], pos[200005];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; i++) scanf("%d", &a[i]), pos[a[i]] = i;
  set<int> cur;
  cur.insert(0);
  cur.insert(n + 1);
  int ans = 0;
  for (int i = n; i >= 1; i--) {
    int p = pos[i];
    int l = *(--cur.lower_bound(p));
    int r = *cur.lower_bound(p);
    if (p - l <= r - p) {
      for (int j = l + 1; j < p; j++)
        if (p < pos[i - a[j]] && pos[i - a[j]] < r) ans++;
    } else {
      for (int j = p + 1; j < r; j++)
        if (l < pos[i - a[j]] && pos[i - a[j]] < p) ans++;
    }
    cur.insert(p);
  }
  printf("%d\n", ans);
}
