#include <bits/stdc++.h>
using namespace std;
int sum[100000];
int main() {
  long long a;
  cin >> a;
  vector<int> v;
  for (int g = 0; g < a; g++) {
    int m;
    cin >> m;
    if (sum[m] == 0) v.push_back(m);
    sum[m]++;
  }
  if (v.size() < 3) {
    cout << "NO";
    return 0;
  }
  sort(v.begin(), v.end());
  for (int g = 0; g < v.size() - 2; g++)
    if (v[g] + 1 == v[g + 1] && v[g] + 2 == v[g + 2]) {
      cout << "YES";
      return 0;
    }
  cout << "NO";
}
