#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int ara[n];
  for (int i = 0; i < n; i++) cin >> ara[i];
  sort(ara, ara + n);
  int c = 0;
  for (int i = 0; i < n - 2; i++) {
    int f = 1, s = 0, t = 0;
    for (int j = i + 1; j < n; j++) {
      if (fabs(ara[i] - ara[j]) == 1 && s == 0)
        s = 1;
      else if (fabs(ara[i] - ara[j]) == 2 && t == 0)
        t = 1;
    }
    if (f == 1 && s == 1 && t == 1) {
      c = 1;
      break;
    }
  }
  if (c == 1)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
