#include <bits/stdc++.h>
using namespace std;

typedef long long int lli;

int main(){
   lli arr[100 + 10];
   
   lli ans  = 0;
   lli n,current1 = 0,current2;
   scanf("%lld",&n);
   
   for(lli i = 0; i < n; i++)
      cin >> arr[i];
      
   for(lli i = 0; i < n; i++){
      current1 = 1;
      current2 = 1;
      for(lli j = i + 1; j < n; j++){
         if(arr[j] - arr[i] == 1 || arr[j] - arr[i] == 0)
            current1++;
         if(arr[i] - arr[j] == 1 || arr[i] - arr[j] == 0)
            current2++;
      }
      
      current1 = max(current1,current2);
      ans = max(ans,current1);
   }
   
   cout << ans << endl;
}