#include <bits/stdc++.h>
#define ALL(a) (a).begin(), (a).end()
#define FOR(x,n) for(int x = 0; x < n; x++)
#define SZ(a) ((int)(a).size())
using namespace std;

const int MXA = 100;
int A[MXA] = {};

int main() {
  int N; cin >> N;
  FOR(x,N) {int tmp; cin >> tmp; A[tmp]++; }
  int mx = 0;
  for(int x = 1; x+1 < MXA; x++) mx = max(mx, A[x]+A[x+1]);
  
  cout << mx << "\n";
}