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