#include <bits/stdc++.h>
using namespace std;
int main() {
  long long n, arr[100001], z = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> arr[i];
  }
  sort(arr, arr + n);
  for (int i = 0; i < n; i++) {
    for (int j = i + 1; j < n; j++) {
      if (arr[i] == arr[j]) {
        arr[j] = -1;
      }
    }
  }
  sort(arr, arr + n);
  for (int i = 1; i < (n - 1); i++) {
    if (arr[i] - arr[i - 1] == 1 && arr[i + 1] - arr[i] == 1) {
      cout << "YES" << endl;
      return 0;
    }
  }
  cout << "NO" << endl;
  return 0;
}
