#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;
  int a[n];
  vector<int> ans;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  ans.push_back(a[0]);
  for (int i = 1; i < n; i++) {
    if (a[i] != ans.back()) ans.push_back(a[i]);
  }
  bool got = false;
  int len = ans.size();
  for (int i = 0; i < len - 2; i++) {
    if ((ans[i + 1] - ans[i] < 3 && ans[i + 2] - ans[i] < 3 &&
         ans[i + 2] - ans[i + 1] < 3)) {
      got = true;
      break;
    }
  }
  cout << (got ? "YES\n" : "NO\n");
  return 0;
}
