#include <iostream>

 #include <cstdio>

 #include <cstring>

 #include <algorithm>

 #include <string>

 #include <vector>

 #include <map>

 #include <set>

 #include <queue>

 #include <deque>

 #define FRER() freopen("in.txt", "r", stdin)

 #define FREW() freopen("out.txt", "w", stdout)

 #define INF 0x3f3f3f3f

 using namespace std;

 const int maxn = 1e5 + ;

 char s[maxn], ans[maxn];

 int main()

 {

     //FRER();

     //FREW();

     ios::sync_with_stdio();

     cin.tie();

     int n, d, m, idx;

     while(cin >> n >> d && (n || d)) {

         cin >> s;

         m = n - d;

         idx = ;

         ans[idx] = s[];

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

             while(d && idx >=  && ans[idx] < s[i]) {

                 --idx;

                 --d;

             }

             ans[++idx] = s[i];

         }

         ans[m] = '\0';

         cout << ans << endl;

     }

     return ;

 }