P1106 删数问题

// Problem: P1106 删数问题
// Contest: Luogu
// URL: https://www.luogu.com.cn/problem/P1106
// Memory Limit: 125 MB
// Time Limit: 1000 ms
// User: Pannnn
 
#include <bits/stdc++.h>
 
using namespace std;
 
template<class T>
void debugVector(const T &a) {
    cout << "[ ";
    for (size_t i = 0; i < a.size(); ++i) {
        cout << a[i] << (i == a.size() - 1 ? " " : ", ");
    }
    cout << "]" << endl;
}
 
template<class T>
void debugMatrix2(const T &a) {
    for (size_t i = 0; i < a.size(); ++i) {
        debugVector(a[i]);
    }
}
 
template<class T>
using matrix2 = vector<vector<T>>;
 
template<class T>
vector<vector<T>> getMatrix2(size_t n, size_t m, T init = T()) {
    return vector<vector<T>>(n, vector<T>(m, init));
}
 
template<class T>
using matrix3 = vector<vector<vector<T>>>;
 
template<class T>
vector<vector<vector<T>>> getMatrix3(size_t x, size_t y, size_t z, T init = T()) {
    return vector<vector<vector<T>>>(x, vector<vector<T>>(y, vector<T>(z, init)));
}
 
vector<int> genBigInteger(string a) {
    vector<int> res;
    for (int i = a.size() - 1; i >= 0; --i) {
        res.push_back(a[i] - '0');
    }
    return res;
}
 
void printBigInteger(vector<int> a) {
    for (size_t i = a.size() - 1; i >= 0; --i) {
        cout << a[i];
    }
}
 
vector<int> addBigInteger(vector<int> a, vector<int> b) {
    vector<int> res;
    int pre = 0;
    for (size_t i = 0; i < a.size() || i < b.size() || pre; ++i) {
        if (i < a.size()) pre += a[i];
        if (i < b.size()) pre += b[i];
        res.push_back(pre % 10);
        pre /= 10;
    }
    return res;
}
 
void deletePreZero(string &str) {
    if (str.size() == 0) {
        str = "0";
    }
    while (str.size() > 1 && str[0] == '0') {
        str.erase(str.begin());
    }
}
 
void nextN(string &str) {
    for (int i = 0; i < str.length() - 1; ++i) {
        if (str[i] > str[i + 1]) {
            str.erase(str.begin() + i);
            return;
        }
    }
    str.erase(str.end() - 1);
    return;
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    
    // 先删除最靠左的 n[i] > n[i + 1]的那个数字
    // 否则删除最后一个
    
    string str;
    cin >> str;
    
    int k;
    cin >> k;
    while (k--) {
        nextN(str);
    }
    deletePreZero(str);
    cout << str << endl;
    return 0;
}