#include <bits/stdc++.h>
#define INF 100000009
#define mod 1000000007
#define PI 3.14159
#define vi vector<int>
#define ll long long
#define ii pair<int, int>
#define vii vector<ii>
#define pb push_back
#define mp make_pair
#define fs first
#define sc second
#define mt make_tuple
#define eb emplace_back
#define CLR(arr) memset(arr, 0, sizeof(arr))
#define FAST_IO ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
using namespace std;

int A[1000];
int main()
{
    int n;
    cin>>n;
    for(int i=0; i<n; ++i)
    {
        int x;
        scanf("%d", &x);
        A[x]++;
    }
    int ans = 0;
    for(int i=1; i<=100; ++i)
        ans = max(A[i-1]+A[i], ans);
    cout<<ans<<endl;
    return 0;
}