#include<bits/stdc++.h>
using namespace std;
#define Fr(i,a,b) for(int i=a;i<=b;i++)
#define For(i,a,b) for(int i=a;i<b;i++)
#define Frd(i,a,b) for(int i=a;i>=b;i--)
#define Ford(i,a,b) for(int i=a;i>b;i--)
#define bit1(x) __builtin_popcountll(x)
#define fi first
#define se second
#define maxn 1000
typedef long long ll;
typedef pair<int,int> ii;
const int mod=1e9+7;
const int oo=INT_MAX;
int n,a[maxn],b[maxn],ans;

int main()
{
    scanf("%d",&n);
    Fr(i,1,n)
    {
        scanf("%d",&a[i]);
        ++b[a[i]];
    }
    Fr(i,1,n) ans=max(ans,b[a[i]]+b[a[i]+1]);
    printf("%d",ans);
	return 0;
}