/*
jai shree ram _/\_
A hacker from NITP
*/
 
#include<bits/stdc++.h>
using namespace std;
 
#define mod 1000000007
typedef set<string> ss;
typedef vector<int> vs;
typedef map<int,char> msi;
typedef pair<int,int> pa;
typedef long long int ll;
 
int i,n,a[102],j,cnt[102],ans;
int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */  
    //freopen("inputf.in", "r", stdin);
  	//freopen("o.out", "w", stdout);
	ios_base::sync_with_stdio(false);
	cin.tie(0);
    memset(cnt,0,sizeof(cnt));
    cin>>n;
    for(i=0;i<n;i++)
        cin>>a[i],cnt[a[i]]++;
    ans=0;
    for(i=1;i<=100;i++)
        {
        ans=max(ans,cnt[i]+cnt[i+1]);
    }
    cout<<ans<<"\n";
    return 0;
}