#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int arr[n];
  for (int i = 0; i < n; i++) cin >> arr[i];
  sort(arr, arr + n);
  bool p = false;
  for (int i = 0; i < n - 2; i++) {
    if (arr[i] + arr[i + 1] > arr[i + 2]) {
      p = true;
      break;
    }
  }
  if (p)
    cout << "YES" << endl;
  else
    cout << "NO" << endl;
}
