A.cpp

#include <bits/stdc++.h>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define EACH(it,a) for(__typeof(a.begin()) it = a.begin(); it != a.end(); ++it)

#define DEBUG(x) { cout << #x << " = "; cout << (x) << endl; }
#define PR(a,n) { cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl; }
#define PR0(a,n) { cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl; }

#define sqr(x) ((x) * (x))
#define ll long long
#define SZ(X) ((int) ((X).size()))
using namespace std;

string s;
int k;

int main() {
    ios :: sync_with_stdio(false);
    while (cin >> s >> k) {
        int n = s.length();
        int last = -1, need = n - k;
        string res = "";
        FOR(i,1,need) {
            int from = last + 1, to = n - (need - i) - 1;

            int u = max_element(s.begin() + from, s.begin() + to + 1) - s.begin();
            last = u;

            res += s[u];
        }
        cout << res << endl;
    }
}