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


int main() {
    int n;
    cin>>n;
    int a[n];
    int b[100]={0};
    for(int i=0;i<n;i++){
        cin>>a[i];
        b[a[i]]++;
    }
    int m=0;
    for(int i=1;i<100;i++){
        if(m<(b[i]+b[i-1])){
            m=b[i-1]+b[i];
        }
        if(m<(b[i]+b[i+1])){
            m=b[i]+b[i+1];
        }
    }
    cout<<m;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}