#include <bits/stdc++.h>
using namespace std;
 
 
typedef long long ll;
typedef vector <int> vi;
typedef pair< int ,int > pii;
typedef istringstream iss;
typedef ostringstream oss;
#define pb push_back
#define mp make_pair
#define f first
#define s second
#define sz size()
#define ln length()
#define rep(i,n) for(int i=0;i<n;i++)
#define fu(i,a,n) for(int i=a;i<=n;i++)
#define fd(i,n,a) for(int i=n;i>=a;i--)
#define all(a)  a.begin(),a.end() 
#define ESP (1e-9)
 
#define gi(n) scanf("%d",&n)
#define gl(n) cin >> n
#define pi(n) printf("%d",n)
#define pl(n) cout << n
#define ps printf(" ")
#define pn printf("\n")
#define dg(n,s); printf("%s %d",s,n)
#define imax numeric_limits<int>::max()
#define imin numeric_limits<int>::min()
#define lmax numeric_limits<ll>::max()
#define lmin numeric_limits<ll>::min()

map < int , int > m1 ; 
int n , x ; 
int main() {
     cin >> n ;
     while(n--){
          cin >> x ;
          m1[x]++ ; 
     }
    int ans = 2 ; 
      for (int i = 0 ; i <= 100 ; i++){
           ans = max (ans , m1[i] + m1[i+1]) ;
      }
    cout << ans ; 
}