#include <bits/stdc++.h>
using namespace std;
int n;
map<int, int> num;
int main() {
  cin >> n;
  int minNum = 1000 * 1000 * 1000 + 1;
  for (int i = 0; i < n; i++) {
    int tmp;
    cin >> tmp;
    num[tmp]++;
    minNum = min(minNum, tmp);
  }
  for (int i = minNum; n > 0; i++) {
    if (num[i] == 0 || num[i] > num[i + 1]) {
      cout << "NO" << endl;
      return 0;
    }
    num[i + 1] -= num[i];
    n -= 2 * num[i];
  }
  cout << "YES" << endl;
  return 0;
}
