krsu_736.cpp

#include <bits/stdc++.h>

using namespace std;

int main()
{
    int b;
    string a, d;
    cin >> a;
    cin >> b;
    d = a;
    sort(d.begin(), d.end());
    int c = 0;
    bool e[b];

    for (int i = 0; i < a.size(); i++){
        bool found = false;
        if (c < b){
            for (int j = 0; j < b; j++){
                if (!found) found = d[j] == a[i];
                if (found) e[i] = true;
            }
        }
        if (found) c++;
        else if (!e[i]) cout << a[i];
    }

    return 0;
}