#include <bits/stdc++.h>
using namespace std;
vector<int> o, e;
map<int, int> M;
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int x;
    scanf("%d", &x);
    if (x & 1)
      o.push_back(x);
    else
      e.push_back(x);
    M[x]++;
  }
  sort(o.begin(), o.end());
  sort(e.begin(), e.end());
  if (o.size() != e.size()) {
    printf("NO\n");
    return 0;
  }
  n /= 2;
  if (o[0] < e[0]) {
    for (int i = 0; i < n; i++) {
      if (abs(o[i] - e[i]) != 1) {
        printf("NO\n");
        return 0;
      }
      if (i && abs(o[i] - e[i - 1]) != 1) {
        printf("NO\n");
        return 0;
      }
    }
  } else {
    for (int i = 0; i < n; i++) {
      if (abs(o[i] - e[i]) != 1) {
        printf("NO\n");
        return 0;
      }
      if (i && abs(e[i] - o[i - 1]) != 1) {
        printf("NO\n");
        return 0;
      }
    }
  }
  for (int i = min(o[0], e[0]) + 1; i < max(o.back(), e.back()); i++) {
    if (M[i] < 2) {
      printf("NO\n");
      return 0;
    }
  }
  printf("YES\n");
  return 0;
}
