#include 

using namespace std;
class Array {
private:
    int capacity;
    int at;
    int *arr;
public:
    Array(int _capacity) {
        capacity = _capacity;
        at = 0;
        arr = new int[capacity];
    }
    ~Array() {
        
    }
    void add(int x) {
        if(at == capacity) {
            int *tmp_arr = new int[capacity];
            for(int i = 0; i < at; i++) {
                tmp_arr[i] = arr[i];
            }
            capacity *= 2;
            arr = new int[capacity];
            for(int i = 0; i < at; i++) {
                arr[i] = tmp_arr[i];
            }
        }
        arr[at] = x;
        at++;
    }
    void change(int a, int b) {
        for(int i = 0; i < at; i++) {
            if(arr[i] == a) {
                arr[i] = b;
            }
        }
    }
    void deleteAll(int x) {
        int *tmp_arr = new int[capacity];
        int tmp_at = 0;
        for(int i = 0; i < at; i++) {
            if(arr[i] != x) {
                tmp_arr[tmp_at] = arr[i];
                tmp_at++;
            }
        }
        arr = new int [capacity];
        for(int i = 0; i < tmp_at; i++) {
            arr[i] = tmp_arr[i];
        }
        at = tmp_at;
    }
    void print() {
        for(int i = 0; i < capacity; i++) {
            if(i < at) {
                cout << arr[i] << " ";
            }
            else {
                cout << " _ ";
            }
        }
        cout << endl;
    }
};
int main() {
    Array a(5);
    a.add(2);
    a.add(3);
    a.add(4);
    a.print();
    
    a.add(5);
    a.add(6);
    a.print();
    
    a.add(7);
    a.print();
   
    
    a.change(2, 10);
    a.print();
    
    a.deleteAll(5);
    a.print();
    return 0;
}