#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int n, i, j, ans, temp, a[105];
    cin>>n;
    for(i=0;i<105;i++){
        a[i]=0;
    }
    for(i=0;i<n;i++){
        cin>>temp;
        a[temp]++;
    }
    ans = a[0]+a[1];
    for(i=1;i<104;i++){
        if(a[i]+a[i+1]>ans){
            ans = a[i]+a[i+1];
        }
    }
    cout<<ans<<endl;
    return 0;
}