#include<bits/stdc++.h>
#define ll long long int
#define mod 1000000007
#define MX 100009
#define ff first
#define ss second
#define mp make_pair
#define pb(a) push_back(a)
#define pii pair<ll,ll>
using namespace std;

ll A[MX];
bool visit[MX];

int main()
{
    ll t,T,n,m,i,j,k,ans,a,b,c,x,y,l,r;
    string ss;
//    while(scanf("%lld %lld %lld",&n,&m,&k)!=EOF)
    while(scanf("%lld",&n)!=EOF)
    {
        ans=0;
        memset(A,0,sizeof A);
        for(i=1; i<=n; i++)
        {
            scanf("%lld",&a);
            A[a]++;
        }
        for(i=1; i<=100; i++)
        {
            ans=max(ans,A[i]+A[i+1]);
        }


        printf("%lld\n",ans);
    }
    return 0;
}