#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, t;
  vector<int> v;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> t;
    if (find(v.begin(), v.end(), t) == v.end()) v.push_back(t);
  }
  sort(v.begin(), v.end());
  for (int i = 2; i < v.size(); i++)
    if (v[i] - v[i - 1] <= 2 && v[i] - v[i - 2] <= 2 &&
        v[i - 1] - v[i - 2] <= 2 && v[i - 2] != v[i - 1] && v[i - 1] != v[i])
      return printf("YES\n") * 0;
  cout << "NO" << endl;
  return 0;
}
