//Ansh Khanna
#include<bits/stdc++.h>
#define ll long long
#define ld long double
#define fi first
#define se second
using namespace std;
#define sd(x) scanf("%d",&x)
#define pd(x) printf("%d",x)
#define sl(x) scanf("%lld",&x)
#define pl(x) printf("%lld",x)
#define mem(x,a) memset(x,a,sizeof(x))
#define pii pair<int,int>
#define mp make_pair
#define pb push_back
#define all(v) v.begin(),v.end()
#define N (int)(1e5+5)
int cnt[N];
void solve(){
    int n;
    sd(n);
    for(int i=1;i<=n;i++){
        int x;
        sd(x);
        cnt[x]++;
    }
    int ans=0;
    for(int i=2;i<=200;i++){
        ans=max(ans,cnt[i]+cnt[i-1]);
    }
    cout<<ans;
}
int main(){
   //freopen("input.IN","r",stdin);
   //freopen("out.txt","w",stdout);
   int t=1;
   //sd(t);
   //ios_base::sync_with_stdio(false);
   for(int i=1;i<=t;i++){
       //printf("Case #%d: ",i);
       solve();
   }
   return 0;
}