#include <bits/stdc++.h>
using namespace std;
int n, b, i, j;
int main() {
  cin >> n;
  int a[n], d[n + 1];
  for (i = 0; i < n; ++i) {
    cin >> a[i];
    d[a[i]] = i;
  }
  set<int> s = {-1, n};
  for (i = n; i > 0; --i) {
    auto t = s.upper_bound(d[i]);
    int r = *t-- - 1, l = *t + 1;
    s.insert(d[i]);
    if (2 * d[i] - l < r)
      for (j = l; j < d[i]; ++j)
        b += !(d[i - a[j]] < d[i]) & (d[i - a[j]] <= r);
    else
      for (j = r; j > d[i]; --j) b += (d[i - a[j]] >= l) & (d[i - a[j]] < d[i]);
  }
  cout << b;
}
