#include <bits/stdc++.h>
using namespace std;
int rint() {
  int x;
  scanf("%d", &x);
  return x;
}
int main() {
  int n = rint();
  set<int> v;
  for (int i = (0); i < (n); ++i) v.insert(rint());
  for (set<int>::iterator it = v.begin(); it != v.end(); ++it) {
    set<int>::iterator iit = it;
    ++iit;
    if (iit != v.end()) {
      set<int>::iterator iiit = iit;
      ++iiit;
      if (iiit != v.end()) {
        if (*it + 1 == *iit && *iit + 1 == *iiit) {
          printf("YES");
          return 0;
        }
      }
    }
  }
  printf("NO");
  return 0;
}
