#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define pb push_back
#define fr first
#define sc second
#define ARRS int(4e5+11)
#define MAX ((long long)(1e18))
#define HS1 ((long long)(1000001329))
#define HS2 ((long long)(1000001531))
#define MOD ((long long)1000000007)

ll i,j,l,k,n,m,p,c[ARRS],d,mx,mn,x,y,ans,res,sum;
ll a[ARRS];
ll fx[ARRS];
//string s,s1,s2;
vector<ll> v[ARRS];
double tx,ty;

int main(){
    #ifdef KHOKHO
        freopen("in.in","r",stdin);
        freopen("out.out","w+",stdout);
    #endif //KHOKHO
    cin>>n;
    for(int i=0; i<n; i++){
        cin>>k;
        fx[k]++;

    }
    ll pas=0;
    for(int i=1; i<=100; i++){
        pas=max(pas,fx[i]+fx[i-1]);
    }
    cout<<pas;
    return 0;
}