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