#include <bits/stdc++.h>
using namespace std;
int n;
const int M = 1e5 + 7;
int size = 0;
class Node
{
public:
    int back, size;
} q[M];
int a[M];
void insert(int k)
{
    int flag = 0;
    for (int i = 1; i <= size; i++)
    {
        if (q[i].back == k - 1)
            if (q[i].size < q[flag].size || flag == 0)
                flag = i;
    }
    if (!flag)
    {
        size++;
        q[size].back = k;
        q[size].size = 1;
    }
    else
    {
        q[flag].back = k;
        q[flag].size++;
    }
    return;
}
inline void solve(void)
{
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
    sort(a + 1, a + n + 1);
    for (int i = 1; i <= n; i++)
    {
        insert(a[i]);
    }
    int ans = INT_MIN;
    for (int i = 1; i <= size; i++)
    {
        ans = max(ans, q[i].size);
    }
    cout << ans;
    return;
}
int main()
{
    // freopen(".in","r",stdin);
    // freopen(".out","w",stdout);
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    solve();

    return 0;
}