#include <bits/stdc++.h>
using namespace std;
int a[55];
int b[55];
map<int, bool> mp;
int main() {
  int n, j = 0, x;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
    mp[a[i]] = true;
  }
  for (int i = 0; i < n; i++) {
    if (mp[a[i]] == true) {
      b[j] = a[i];
      j++;
      mp[a[i]] = false;
    }
  }
  sort(b, b + j);
  for (int i = 0; i < j; i++) {
    if ((b[i] == b[i + 1] - 1) && (b[i] == b[i + 2] - 2)) {
      cout << "YES";
      goto ed;
    }
  }
  cout << "NO";
ed:
  return 0;
}
