#include<bits/stdc++.h>

using namespace std;


int main(){
    int n,count,countmax=1,i=1,k=0,flag=0;
    cin >> n;
    int a[n];
    for(int a_i = 0;a_i < n;a_i++){
       cin >> a[a_i];
    }
    sort(a,a+n);
    while(k<n)
        {
        count=1;
    while((a[i]==a[k]||a[i]==a[k]+1)&&i<n)
        {
        count++;
        i++;
        flag=1;
    }
        if(count>countmax)
            countmax=count;
        k=i;
        i++;
    }
    if(flag!=0)
    cout<<countmax;
    else
        cout<<0;
    return 0;
}