#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int a[n];
  bool c = false;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  int j = 1;
  for (int i = 0; i + j < n; i++) {
    j = 1;
    while (a[i] == a[i + j]) {
      a[i + j] = 1010;
      j++;
    }
  }
  sort(a, a + n);
  for (int i = 0; i < n - 2; i++) {
    if (a[i] + 1 == a[i + 1] && a[i] + 2 == a[i + 2]) {
      c = true;
    }
  }
  if (c) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  return 0;
}
