#include <cstdio>
#include <cstring>
#include <iostream>
#include <math.h>
#include <string>
#include <sstream>
#include <iomanip>
#include <stdio.h>
#include <stdlib.h>
#include <ctime>
#include <time.h>
#include <string.h>
#include <algorithm>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
using namespace std;

const int off = 1<<19;

int T[ off*2 ][2];
int n, k;
char in[off];

void fill(){
    scanf("%s", in);
    for( int x = 0; x < n; x++ ){
        T[ off+x ][0] = in[x];
        T[ off+x ][1] = x;
    }
    for( int x = off -1; x > 0; x-- )
        if( T[ x*2 ][0] < T[ x*2+1 ][0] ){
            T[ x ][0] = T[ x*2+1 ][0];
            T[ x ][1] = T[ x*2+1 ][1];
        }else{
            T[ x ][0] = T[ x*2 ][0];
            T[ x ][1] = T[ x*2 ][1];
        }
}
pair<int,int> query( int a, int b, int lo = 0, int hi = off, int p = 1 ){
    if( a >= hi || b <= lo )
        return make_pair(-1,-1);
    if( lo >= a && hi <= b ){
        return make_pair(T[p][0],T[p][1]);
    }
    pair<int,int> aa=query( a,b,lo,(lo+hi)/2,p*2),bb=query( a,b,(lo+hi)/2,hi,p*2+1);
    if( aa.first > bb.first )
        return aa;
    else if( aa.first<bb.first )
        return bb;
    else if( aa.second > bb.second )
        return aa;
    else
        return bb;
}
int main(){
    scanf("%d %d", &n, &k);
    fill();
    pair<int ,int > t;
    for( int x = 0; x < n; x++ ){
        t = query( x, x+k+1 );
        if( k - t.second+x >= 0 ){
            k-= t.second-x;
            x = t.second;
        }
        printf("%c",in[ x ]);
    }
    putchar('\n');
}