#include <bits/stdc++.h>   using namespace std;   int main() {     int n;     cin >> n;     vector<int> v(n);     for (int i = 0; i < n; i++) cin >> v[i];     sort(begin(v), end(v));     v.erase(unique(begin(v), end(v)), end(v));     n = v.size();     for (int i = 2; i < n; i++) {       int a = v[i - 2];       int b = v[i - 1];       int c = v[i];       if (a + 1 == b && b + 1 == c) {         cout <<  YES  << endl;         return 0;       }     }     cout <<  NO  << endl;     return 0;   }   