#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0;i<n;i++)
#define ll  long long int
#define pi pair<ll,ll>
#define pii pair<ll,pi>
#define f first
#define mp make_pair
#define s second
#define pb push_back
#define mod 1000000007

map<int ,int >mpp;
int cnt[107],a[107];
int main(){

   // freopen("input.txt", "r", stdin);
    int maxx=-1;
     int n; cin>>n;
     rep(i,n){
        int x;
        cin>>x;
        cnt[x]++;
     }
    for(int i=0;i<105;i++){
        maxx=max(maxx,cnt[i]+cnt[i+1]);
    }
    cout<<maxx<<endl;

}