#include <bits/stdc++.h>
using namespace std;
long long MOD = 1e9 + 7;
int main() {
  ios_base::sync_with_stdio(0);
  int n;
  cin >> n;
  int a[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" << endl;
      return 0;
      ;
    }
  }
  cout << "NO" << endl;
  return 0;
  ;
  return 0;
}
