#include <bits/stdc++.h>
#define mp make_pair
#define pb push_back
#define pii pair<int,int>
#define LL long long
#define st first
#define nd second
using namespace std;
int b[101],ans=0;
int main(){
    int n,t;
    cin>>n;
    for(int i=0;i<n;++i){
        cin>>t;
        b[t]++;
    }
    for(int i=1;i<=100;++i)
        ans=max(ans,b[i]+b[i-1]);
    cout<<ans<<endl;
}