#include<iostream>

#include<cstdio>

#include<string>

#include<cstring>

#include<algorithm>

using namespace std;

const int maxn = ;

int n,x[maxn];

int cmd,cnt,ans,max_x;

int main(){

    freopen("box.in","r",stdin);

    freopen("box.out","w",stdout);

    ios::sync_with_stdio(false);

    cin>>n;

    for(int i = ;i <= n;i++){

        cin>>cmd;

        x[cmd]++;

        max_x = max(max_x,cmd);

    }

    while(){

        cnt = ;

        for(int i = ;i <= max_x;i++){

            while(x[i] && i >= cnt){

                x[i]--;

                cnt++;

            }

        }

        if(!cnt) break;

        ans += ;

    }

    cout<<ans;

    return ;

}