#include <bits/stdc++.h>
int cmp(const void* x1, const void* x2) { return (*(int*)x1 - *(int*)x2); }
int main() {
  int n, i, j = 0;
  int mass[50], mass_t[50];
  int ch[3];
  scanf("%d", &n);
  for (i = 0; i < n; i++) scanf("%d", &mass[i]);
  qsort(mass, n, sizeof(int), cmp);
  for (i = 0; i < n - 1; i++)
    if (mass[i] != mass[i + 1]) {
      mass_t[j] = mass[i];
      j++;
    }
  mass_t[j] = mass[i];
  for (i = 0; i <= j - 2; i++)
    if (mass_t[i] + 2 == mass_t[i + 1] + 1 &&
        mass_t[i + 1] + 1 == mass_t[i + 2]) {
      printf("YES");
      return 0;
    }
  printf("NO");
  return 0;
}
