#include <bits/stdc++.h>
using namespace std;
map<int, bool> mp;
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    mp[a] = 1;
  }
  for (int i = 0; i < 1010; i++) {
    if (mp[i] && mp[i + 1] && mp[i + 2]) {
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
}
