#include <bits/stdc++.h>
using namespace std;
int n, k = 0, flag = 0, a[10000], b[10000];
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> a[i];
  sort(a, a + n);
  for (int i = 0; i < n; i++) {
    if (a[i] != a[i + 1]) {
      b[k] = a[i];
      k++;
    }
  }
  for (int i = 0; i < k; i++) {
    if (b[i + 1] == b[i] + 1 && b[i + 2] == b[i] + 2) {
      cout << "YES" << endl;
      flag = 1;
      break;
    }
  }
  if (!flag) cout << "NO" << endl;
  return 0;
}
