#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) cin >> v[i];
  sort(begin(v), end(v));
  v.erase(unique(begin(v), end(v)), end(v));
  n = v.size();
  for (int i = 2; i < n; i++) {
    int a = v[i - 2];
    int b = v[i - 1];
    int c = v[i];
    if (a + 1 == b && b + 1 == c) {
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
  return 0;
}
