#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> a;
  for (int i = 0; i < n; ++i) {
    int x;
    cin >> x;
    a.push_back(x);
  }
  sort(a.begin(), a.end());
  for (int i = 0; i <= n - 3; ++i)
    if (a[i] + a[i + 1] > a[i + 2]) {
      cout << "YES";
      return 0;
    }
  cout << "NO";
  return 0;
}
