#include <bits/stdc++.h>
using namespace std;

#define ll long long
#define endl '\n'

const int nn = 2e5 + 17, mod = 1e9 + 7;
int n, k; char A[nn];

void Try() {
    cin >> n >> k;
    for (int i = 1; i <= n; i++) {
        cin >> A[i];
    }
    
    for (int i = 1; i + k - 1 <= n; i += k) {
        int j = i + k - 1;
        sort(A + i, A + j + 1);
    }
    
    for (int i = 1; i <= n; i++) {
        cout << A[i];
    }
    
    cout << endl;
}

int32_t main() {
    ios_base::sync_with_stdio(0); cin.tie(0);

    int t = 1;
    //cin >> t;
    for (int i = 1; i <= t; i++) {
        Try();
    }

}