//#define WYTE 133
#include<bits/stdc++.h>
#define X first
#define Y second
#define mp(x,y) make_pair((x),(y))
#define pb(x) push_back(x)
#define eb emplace_back
#define ALL(x) (x).begin(),(x).end()
#define INIT(x,y) memset((x),(y),sizeof(x))
#define arrayin(a,n) for(int i=0;i<n;i++){cin>>a[i];}
#define arrayin1(a,n) for(int i=1;i<=n;i++){cin>>a[i];}
#define arrayout(a,n) for(int i=0;i<n;i++){cout<<a[i]<<" \n"[i+1==n];}
#define arrayout1(a,n) for(int i=1;i<=n;i++){cout<<a[i]<<" \n"[i+1>n];}
#define PQ priority_queue
#define IT iterator
#define INF 1e9
#define LLNF 1e18
#define EPS 1e-9
#define MOD 1000000007
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vii;

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    int n,cnt[105]={},a,i,ans=1;
    cin>>n;
    for(i=0;i<n;i++)
    {
        cin>>a;
        cnt[a]++;
    }
    for(i=1;i<100;i++)
    {
        ans=max(ans,cnt[i]+cnt[i-1]);
    }
    cout<<ans<<"\n";
}