Apagando e Ganhando - Neps

#include <iostream>
#include <cstdio>
#include <stdio.h>
#include <stack>
#include <list>
#include <vector>
#include <cmath>
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <string.h>
#include <sstream>
#include <bitset>
#include <algorithm>
#include <queue>

using namespace std;

int main(){

    string s;
    int c, d;
    cin >> c >> d;
    while (c+d){
        stack<pair<int, int>> n;
        pair<int, int> a;
        cin >> s;
        for (int i = 0; i < (int) s.size(); ++i) {
            if(!i){
                a.first = s[i]-'0';
                a.second = i;
                n.push(a);
            }else{
                if (s[i]-'0' > n.top().first) {
                    while (!n.empty() && d != 0 && s[i]-'0' > n.top().first) {
                        s[n.top().second] = 'x';
                        n.pop();
                        d--;
                    }
                    a.first = s[i]-48;
                    a.second = i;
                    n.push(a);
                    if (!d) {
                        break;
                    }
                } else {
                    a.first = s[i]-48;
                    a.second = i;
                    n.push(a);
                }
            }
        }
        while(d!=0){
            s[n.top().second] = 'x';
            n.pop();
            d--;
        }
        for (int i = 0; i < (int) s.size(); ++i) {
            if(s[i] != 'x'){
                cout << s[i];
            }
        }
        cout << '\n';

        cin >> c >> d;
    }


    system("pause");
    return 0;
}