#include <bits/stdc++.h>
using namespace std;
int main() {
  set<int> s;
  vector<int> v;
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    s.insert(a);
  }
  for (auto it = s.begin(); it != s.end(); it++) {
    v.push_back(*it);
  }
  if (v.size() < 3) {
    cout << "NO" << endl;
  } else {
    for (int i = 0; i < v.size() - 2; i++) {
      if (v[i + 2] - v[i] <= 2 && v[i + 2] - v[i + 1] == 1 &&
          v[i + 1] - v[i] == 1) {
        cout << "Yes" << endl;
        return 0;
      }
    }
    cout << "No" << endl;
  }
}
