#include <bits/stdc++.h>

using namespace std;

map <int, int> mp;
vector <int> a;

int main()
{
  int n;
  scanf("%d", &n);
  
  for (int i = 0; i < n; ++i) {
    int x;
    scanf("%d", &x);
    mp[x]++;
    a.push_back(x);
  }
  
  int res = 0;
  for (int i = 0; i < n; ++i) {
    res = max(res, mp[a[i]] + mp[a[i] - 1]);
    res = max(res, mp[a[i]] + mp[a[i] + 1]);
  }
  
  printf("%d\n", res);
  return(0);
}