#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[100010];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (int i = 1; i < n - 1; i++) {
    if (a[i - 1] + a[i] > a[i + 1]) {
      cout << "YES";
      return 0;
    }
  }
  cout << "NO";
  return 0;
}
