#include <bits/stdc++.h>
using namespace std;
set<long long> gera_primos(long long n) {
  set<long long> primos;
  vector<bool> crivo(n + 1);
  primos.insert(2);
  for (long long i = 3; i <= n; i += 2) {
    if (crivo[i]) continue;
    primos.insert(i);
    for (long long j = i; j <= n; j += i) {
      crivo[j] = true;
    }
  }
  return primos;
}
struct Link {
  long long from, to, t;
};
struct Node {
  bool visitado = false;
  bool cor = false;
  vector<long long> in, out;
};
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  cout.tie(0);
  long long n;
  cin >> n;
  vector<long long> a(n);
  map<long long, long long> d;
  for (auto &x : a) {
    cin >> x;
    d[x]++;
  }
  for (long long i = 1; i < (long long)1000 + 1; i++) {
    long long x = i;
    if (d[x] and d[x + 1] and d[x + 2]) {
      puts("YES");
      return 0;
    }
  }
  puts("NO");
}
