#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;
    cin>>n;
    vector<int> arr;
    int ans = 0;
    for(int i = 0;i<n;i++){
        int x;cin>>x;
        int cnt = 0;
        for(int j = 0;j<arr.size();j++)
            cnt += (x-arr[j] <= 1 && x-arr[j]>=0);
        ans = max(ans, cnt+1);
        cnt = 0;
        for(int j = 0;j<arr.size();j++)
            cnt += (arr[j]-x <= 1 && arr[j]-x >= 0);
        ans = max(ans, cnt+1);
        arr.push_back(x);
    }
    cout<<ans<<endl;
    return 0;
}