import java.util.*;
class main{
    public static void main(String[] args){
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        if(n<0){
            System.out.print("Invalid input");
            return;
        }
        int arr[]=new int[n];
        for(int i=0;i<n;i++){
            if(!sc.NextInt()){
                System.out.print("Invalid input");
                return;
            }
            arr[i]=sc.nextInt();
        }
        int left=0;
        int maxlength=0;
        Map<Integer,Integer>freq=new HashMap<>();
        for(int i=0;i<n;i++){
            freq.put(arr[i],freq.getOrDefault(arr[i],0)+1);
            while(freq.size()>2){
                freq.put(arr[left],freq.get(arr[left])-1);
                if(freq.get(arr[left])==0){
                    freq.remove(arr[left]);
                }
                left++;
            }
            maxlength=Math.max(maxlength,i-left+1);
        }
        System.out.print(maxlength);
    }
}