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