ISLAND HSGTPVinh L9 2019-2020

#define task "ISLAND"

#include <iostream>
#include <cstdio>

using namespace std;

using ll = long long;
using ld = long double;

constexpr int N = 3e6 + 5;
int n, a[N], cnt[N];

void Read()
{
    cin >> n;

    for (int i = 1; i <= n; ++i)
    {
        cin >> a[i];
        ++cnt[a[i]];
    }
}

void Solve()
{
    int ans(0);

    for (int i = 1; i < N; ++i)
        ans += (cnt[i] + i - 1) / i;

    cout << ans;
}

int32_t main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen(task ".INP", "r"))
    {
        freopen(task ".INP", "r", stdin);
        freopen(task ".OUT", "w", stdout);
    }

    Read();
    Solve();
}