#include <bits/stdc++.h>
using namespace std;
long long power(int x, int y) {
  if (y == 0)
    return 1;
  else if (y & 1)
    return x * power(x * x, y / 2);
  else
    return power(x * x, y / 2);
}
int main() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (auto i = 0; i < n; i += 1) cin >> v[i];
  sort(v.begin(), v.end());
  int f = 0, l = 0;
  for (auto i = 1; i < n; i += 1) {
    if (v[i] - v[i - 1] == 1)
      l++;
    else if (v[i] != v[i - 1])
      l = 0;
    if (l == 2) {
      f = 1;
      break;
    }
  }
  if (f)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
