#include <bits/stdc++.h>
using namespace std;
const long long inf = 1000000000000000000LL;
const int MAX = 55;
int N;
int t[MAX];
int main(void) {
  scanf("%d", &N);
  for (int i = (0); i < (N); ++i) scanf("%d", t + i);
  for (int i = (0); i < (N); ++i)
    for (int j = (i + 1); j < (N); ++j)
      for (int k = (j + 1); k < (N); ++k) {
        vector<int> v = {t[i], t[j], t[k]};
        sort(v.begin(), v.end());
        if (v[2] - v[0] > 2) continue;
        if (v[0] == v[1] || v[1] == v[2]) continue;
        puts("YES");
        exit(0);
      }
  puts("NO");
  return 0;
}
