#include <bits/stdc++.h>
using namespace std;
bool calc(vector<int>& v, int n) {
  if (n <= 1) {
    return true;
  }
  if (v.size() == 2) {
    if (v[0] + 1 == v[1]) {
      return true;
    } else {
      return false;
    }
  }
  vector<int>::iterator it = find(v.begin(), v.end(), v[v.size() - 1] - 1);
  if (it != v.end() && (*(it + 1) == *it || *(it - 1) == *it)) {
    v.erase(it);
    v.pop_back();
    return calc(v, n - 2);
  } else {
    return false;
  }
}
int main() {
  int n;
  while (cin >> n) {
    vector<int> v(n);
    for (int i = 0; i < n; i++) {
      cin >> v[i];
    }
    sort(v.begin(), v.end());
    if (v.size() % 2 == 1) {
      cout << "NO" << endl;
    } else {
      if (calc(v, n)) {
        cout << "YES" << endl;
      } else {
        cout << "NO" << endl;
      }
    }
  }
  return 0;
}
