#include <cstdio>
#include <cstring>
#include <cassert>
#include <algorithm>
#include <iostream>
#include <vector>

using namespace std;

#define TRACE(x) cerr << #x << " = " << x << endl
#define REP(i, n) for (int i=0; i<n; i++)
#define FOR(i, a, b) for (int i=(a); i<(b); i++)

typedef long long ll;
typedef pair<int, int> P;
#define X first
#define Y second

const int M = 124;

int p[M];

int main()
{
  int n;
  scanf("%d", &n);
  REP(i, n) {
    int x;
    scanf("%d", &x);
    p[x]++;
  }

  int rje = 0;
  REP(i, M-2)
    rje = max(rje, p[i] + p[i+1]);
  printf("%d\n", rje);

  return 0;
}