#include <bits/stdc++.h>
using namespace std;

typedef vector<int> vii;
typedef vector<long long> vll;

#define MOD (long long)(1e9+7)
#define eps  1e-9
#define ll  long long
#define F first
#define mp make_pair
#define S second
#define fill(a,val) memset(a, (val), sizeof(a))
#define pb push_back
#define fast ios_base::sync_with_stdio(false),cin.tie(0),cout.tie(0)
const int  N  = (1e5 + 9);
#define INF (long long )(1e9 + 7)


//FILE *fin = freopen("cubes.in","r",stdin);

//FILE *fout = freopen("out.txt","w",stdout);



ll inv(ll a,ll p)
{ ll temp=1;
  while(p!=0)
  { if(p%2==1)
      temp=(temp*a)%INF;
    a=((ll)a*a)%INF;
    p=p/2;
  }
  return temp;
}

int main() {
  fast;
  //FILE *fin = freopen("huffman.in","r",stdin);
  //FILE *fout = freopen("huffman.out","w",stdout);
 int n;
 cin>>n;
 int a[109];
 fill(a,0);
 for(int i=0;i<n;i++){
 	int temp;
 	cin>>temp;
 	a[temp]++;
 }
 ll ans=0;
 for(int i=1;i<99;i++){
 	if(a[i]+a[i+1]>ans) ans=a[i]+a[i+1];
 }
 cout<<ans;
  return 0;
  
}