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

using namespace std;

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

typedef long long llint;

int main(void) {
  int n;
  scanf("%d", &n);

  vector<int> cnt(111);
  REP(i, n) {
    int x;
    scanf("%d", &x);
    cnt[x]++;
  }
  
  int ans = 0;
  REP(i, 100) ans = max(ans, cnt[i]+cnt[i+1]);
  printf("%d\n", ans);
  return 0;
}