#include <bits/stdc++.h>
using namespace std;
int n,a[1000],b[1000],ans;
int main(){
    cin>>n;
    for (int i=1;i<=n;i++){cin>>a[i];b[a[i]]++;}
    for (int i=0;i<100;i++)
        if (b[i]+b[i+1]>ans)ans=b[i]+b[i+1];
        cout<<ans;
    return 0;
}