#include <bits/stdc++.h>
void quicksort(int[], int, int);
int main() {
  int i, j, k, n;
  scanf("%d", &n);
  int ball[n];
  for (i = 0; i < n; i++) {
    scanf("%d", &ball[i]);
  }
  quicksort(ball, 0, n - 1);
  i = 0;
  j = 1;
  k = 2;
  while (i < n - 2) {
    while (ball[i] == ball[j]) {
      j++;
      if (j == n - 1) {
        printf("NO");
        return 0;
      }
    }
    if (ball[j] - ball[i] <= 2) {
      k = j + 1;
      while (ball[j] == ball[k]) {
        k++;
        if (k == n) {
          printf("NO");
          return 0;
        }
      }
      if (ball[k] - ball[j] <= 2 && ball[k] - ball[i] <= 2) {
        printf("YES");
        return 0;
      }
    }
    i = j;
    j = k;
    while (ball[j] == ball[k]) {
      k++;
      if (k == n) {
        printf("NO");
        return 0;
      }
    }
  }
  return 0;
}
void quicksort(int A[], int ini, int fin) {
  int central = (ini + fin) / 2;
  int pivote = A[central];
  int i = ini, j = fin, aux;
  do {
    while (A[i] < pivote) i++;
    while (A[j] > pivote) j--;
    if (i <= j) {
      aux = A[i];
      A[i] = A[j];
      A[j] = aux;
      i++;
      j--;
    }
  } while (i <= j);
  if (ini < j) {
    quicksort(A, ini, j);
  }
  if (fin > i) {
    quicksort(A, i, fin);
  }
}
