#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
  int A[100];
  for(int i = 0; i < 100; ++i) A[i] = 0;
  int N;
  cin >> N;
  for(int i = 0; i < N; ++i) {
    int a;
    cin >> a;
    A[a]++;
  }
  int res = 0;
  for(int j = 0; j < 99; ++j) {
    if(A[j] + A[j + 1] > res) res = A[j] + A[j + 1];
  }
  cout << res << endl;
  return 0;
}