#include <bits/stdc++.h>
using namespace std;
long long int n, t[11111];
int main() {
  cin >> n;
  for (int i = 1; i <= n; ++i) {
    cin >> t[i];
  }
  sort(t + 1, t + n + 1);
  for (int i = 1; i <= n; ++i) {
    for (int j = i + 1; j <= n; ++j) {
      for (int o = i + 2; o <= n; ++o) {
        if (t[i] != t[j] && t[o] - t[j] <= 2 && t[o] - t[j] != 0 &&
            t[j] - t[i] <= 2 && t[j] - t[i] != 0 && t[o] - t[i] <= 2 &&
            t[o] - t[i] != 0) {
          cout << "YES";
          return 0;
        } else {
          continue;
        }
      }
    }
  }
  cout << "NO";
  return 0;
}
