#include <bits/stdc++.h>
#define ff first
#define ss second
#define pb push_back
#define MOD (1000000007LL)
#define LEFT(n) (2*(n))
#define RIGHT(n) (2*(n)+1)
 
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> ii;
typedef pair<int, ii> iii;
 
ll pwr(ll base, ll p, ll mod = MOD){
ll ans = 1;while(p){if(p&1)ans=(ans*base)%mod;base=(base*base)%mod;p/=2;}return ans;
}
 
ll gcd(ll a, ll b){
    if(b == 0)  return a;
    return gcd(b, a%b);
}

typedef vector<double> VD;
typedef vector<VD> VVD;
typedef vector<int> VI;

int n,a[105],b[105];
int main()
{
    cin>>n;
    for(int i=0;i<n;i++)
    {
        cin>>a[i];
        b[a[i]]++;
    }
    int ans = b[1]+b[2];

    for(int i=2;i<=100;i++)
        ans = max(ans,b[i]+b[i+1]);

    cout<<ans<<"\n";
    return 0;
}