#include <bits/stdc++.h>
#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
using namespace std;
const long long inf = numeric_limits<long long>::max() / 2;
const long double eps = 1e-9;
const long double pi = acos(-1);
template <typename T>
inline bool mineq(T& a, T b) {
  return (a > b) ? (a = b, 1) : 0;
}
template <typename T>
inline bool maxeq(T& a, T b) {
  return (a < b) ? (a = b, 1) : 0;
}
inline void solve(), read();
const string file = "";
int main() {
  if (file != "") {
    freopen((file + ".in").c_str(), "r", stdin);
    freopen((file + ".out").c_str(), "w", stdout);
  }
  ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  ;
  read();
  solve();
  return 0;
}
long long n;
vector<long long> a;
vector<pair<long long, long long> > b;
inline void solve() {
  for (long long i = 0; i < n; i++) {
    if (i && a[i] == a[i - 1]) {
      ++b.back().second;
    } else if (i == 0 || a[i] == a[i - 1] + 1) {
      b.push_back({a[i], 1});
    } else {
      cout << "NO"
           << "\n";
      return;
    }
  }
  for (long long i = 0; i < (long long)((b).size()) - 2; i++) {
    b[i + 1].second -= b[i].second;
    if (b[i + 1].second <= 0) {
      cout << "NO"
           << "\n";
      return;
    }
  }
  if (b[(long long)((b).size()) - 1].second !=
      b[(long long)((b).size()) - 2].second) {
    cout << "NO"
         << "\n";
    return;
  }
  cout << "YES"
       << "\n";
}
inline void read() {
  cin >> n;
  a.resize(n);
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort((a).begin(), (a).end());
}
