#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define mp make_pair

const int MAXM = 1e2+4;
int a[MAXM],b[MAXM];

int main()
{
    int n,i,j,k;
    cin>>n;  
    for(i=0;i<n;i++){
        cin>>a[i];
        b[a[i]]++;
    }

    int maxm=0;
    for(i=1;i<100;i++){
        maxm=max(maxm,(b[i]+b[i-1]));
    }

    cout<<maxm<<endl;
    return 0;
}