#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  set<int> set;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int put;
    scanf("%d", &put);
    set.insert(put);
  }
  vector<int> arr(set.size());
  copy(set.begin(), set.end(), arr.begin());
  sort(arr.begin(), arr.end());
  int consq = 0;
  int iter = arr.size();
  for (int i = 1; i < iter; i++) {
    if (arr[i - 1] == arr[i] - 1) {
      consq++;
    } else {
      consq = 0;
    }
    if (consq == 2) {
      printf("YES\n");
      return 0;
    }
  }
  printf("NO\n");
  return 0;
}
