#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define mp make_pair
#define ft first
#define sd second
#define mem(a, v) memset(a, v, sizeof(a))
typedef long long ll;
typedef pair<int, int> PII;
typedef vector<int> VI;
typedef vector<VI> matrix;
const ll MOD = 1000000007LL;

int cnt[100100];

int main()
{
    int n;
    cin>>n;
    for(int i=0; i<n; i++) {
        int x;
        cin>>x;
        cnt[x]++;
    }
    int ans = 0;
    for(int i=1; i<100; i++) {
        ans = max(ans, cnt[i] + cnt[i+1]);
    }
    cout<<ans<<"\n";
    return 0;
}