#include <bits/stdc++.h>
using namespace std;
const int MAX = 200005;
long long a[MAX];
int main() {
  int n;
  cin >> n;
  bool flag = false;
  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] < (a[i - 1] + a[i - 2])) {
      flag = true;
      break;
    }
  }
  if (flag) {
    cout << "yes" << endl;
  } else {
    cout << "no" << endl;
  }
  return 0;
}
