#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  scanf("%d", &n);
  int i, j, c;
  vector<int> v;
  for (i = 0; i < n; i++) {
    scanf("%d", &c);
    v.push_back(c);
  }
  sort(v.begin(), v.end());
  for (i = 0; i < v.size() - 1;) {
    if (v[i] == v[i + 1]) {
      v.erase(v.begin() + i);
    } else
      i++;
  }
  if (v.size() < 3) {
    cout << "NO";
    return 0;
  }
  for (i = 0; i < v.size() - 2; i++) {
    if ((v[i] + 2) == (v[i + 1] + 1) and (v[i + 1] + 1) == v[i + 2]) {
      cout << "YES";
      return 0;
    }
  }
  cout << "NO";
}
