#include <bits/stdc++.h>
#define x first
#define ll long long
#define mk make_pair
#define y second
#define pb push_back
#define pll pair<ll, ll>
#define pii pair<int, int>
#define inf INT_MAXoverl
#define rep(i, a, b) for (int i = a; i <= b; ++i)
#define rrep(i, a, b) for (int i = a; i >= b; i--)
using namespace std;
const int mod = 1e9 + 7;
const int maxn = 1e6 + 5;
int main() {
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  int cnt[200] = {0};
  rep(i, 0, n - 1) {
    int x;
    cin >> x;
    cnt[x]++;
  }
  int mx=0;
  rep(i,0,99)
  {
    mx=max(mx,cnt[i]+cnt[i+1]);
  }
  cout<<mx<<"\n";
  return 0;
}