#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ld = long double;

int N, cnt = 1, same = 0;
ll A[101010];

int main() {
  cin >> N;
  for (int i = 0; i < N; i++) cin >> A[i];
  sort(A, A + N);
  bool flag = false;
  for (int i = 0; i < N - 1; i++) {
    if (!flag && A[i] + 1 == A[i + 1]) {
      flag = true;
      cnt++;
    }
    if (A[i] == A[i + 1]) {
      same++;
      if (same > cnt) cnt++;
    } else same = 0;
  }
  cout << cnt << endl;
  return 0;
}