#include <bits/stdc++.h>
using namespace std;

int main(){
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n;
  cin >> n;

  int temp;
  int cont[110];
  memset(cont,0,sizeof(cont));
  for (int i = 0; i < n; i++){
    cin >> temp;
    cont[temp]++;
  }
  int count = 0;
  for (int i = 0; i < 100; i++){
    if (max(cont[i+1]+cont[i],cont[i]) > count)
      count = cont[i+1]+cont[i];
  }
  cout << count << "\n";
  return 0;
}