#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, *a, i, j = 0, k = 0, f1 = 0, f2 = 0;
  cin >> n;
  a = (int *)malloc(n * sizeof(int));
  for (i = 0; i < n; i++) {
    cin >> a[i];
  }
  sort(a, a + n);
  for (i = 0; i < n - 2; i++) {
    j = i + 1;
    while (j < n - 1) {
      if (a[i] == a[j] - 1) {
        f1 = 1;
        break;
      } else if (a[i] == a[j]) {
        j++;
      } else {
        f1 = 2;
        break;
      }
    }
    if (f1 == 2) {
      f1 = 0;
      continue;
    }
    k = j + 1;
    while (k < n) {
      if (a[j] == a[k] - 1) {
        f2 = 1;
        break;
      } else if (a[j] == a[k]) {
        k++;
      } else {
        f2 = 2;
        break;
      }
    }
    if (f2 == 2) {
      f2 = 0;
      continue;
    }
    if (f1 == 1 || f2 == 1) {
      break;
    }
  }
  if (f1 == 1 && f2 == 1) {
    cout << "YES";
  } else {
    cout << "NO";
  }
  cin >> n;
  return 0;
}
