#include <bits/stdc++.h>
using namespace std;
int n, a[100000];
int main() {
  int i, dung, j, k;
  while (scanf("%d", &n) > 0) {
    for (i = 0; i < n; i++) scanf("%d", &a[i]);
    sort(a, a + n);
    dung = 0;
    for (i = 0; i < n - 2; i++) {
      for (j = i + 1; j < n - 1; j++) {
        for (k = j + 1; k < n; k++) {
          if (a[i] != a[j] && a[j] != a[k]) {
            if (a[j] - a[i] <= 2 && a[k] - a[i] <= 2 && a[k] - a[j] <= 2) {
              printf("YES\n");
              dung = 1;
              k = n;
              j = n;
              i = n;
            }
          }
        }
      }
    }
    if (dung == 0) printf("NO\n");
  }
  return 0;
}
