ABC143A - Curtain

問題：A - Curtain

#include <algorithm>
#include <iostream>
using namespace std;

int main(void) {
    int a, b;

    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> a >> b;
    cout << max(0, a - 2 * b) << "\n";
    return 0;
}