#include <bits/stdc++.h>
using namespace std;
void sol() {
  long long n;
  cin >> n;
  long long a[n + 1];
  vector<long long> v;
  for (long long i = 0; i < n; ++i) cin >> a[i];
  a[n] = 10001;
  sort(a, a + n);
  v.push_back(a[0]);
  for (long long i = 1; i < n + 1; ++i) {
    if (a[i] != a[i - 1]) v.push_back(a[i]);
  }
  for (long long i = 0; i < v.size() - 2; ++i) {
    if ((v[i] == v[i + 1] - 1) && (v[i] == v[i + 2] - 2)) {
      cout << "YES";
      return;
    }
  }
  cout << "NO";
}
int32_t main(void) {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  long long t = 1;
  while (t--) sol();
}
