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