#include <iostream>

using namespace std;

const int maxen = 1000*100*4+109;
int main()
{

    int n; cin >> n;
    int k; cin >> k;
    char str[maxen];
    cin >> str;

    int mass[maxen];

    for(int i = 0; i<n; i++)
    {
        mass[i] = str[i];
    }

    for (int i = 0; i < n-1; i++)
    {
        for (int j = 0; j < n - i - 1; j++)
        {
            if (mass[j] > mass[j + 1])
            {
                swap(mass[j],mass[j+1]);

            }
        }
    }
    int lol[maxen];
    int x = 0;
    int z = 0;
    for (int i = 0; i < k; i++)
    {
        mass[i] = '0';
    }

    for (int i = 0; i < n; i++)
    {
        if(mass[i] != '0')
        {
            lol[i-x] = mass[i];
            z++;
        }
        if(mass[i] == '0')
        {
            x++;
        }

    }
    char ses[maxen];
    for (int i = 0; i < z; i++)
    {
        lol[i] = ses[i];
    }


    for(int i = 0; i < z; i++)
    {
        cout << ses[i];
    }




}