题解 | 清楚姐姐买竹鼠

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
     public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long a = in.nextLong();
        long b = in.nextLong();
        long x = in.nextLong();

        if ( b / 3 < a) {
            long cost = x % 3;
            if (cost == 0) {
                System.out.println((x / 3) * b);
            } else if (cost * a < b){
                System.out.println((x / 3) * b + cost * a);
            }else {
                System.out.println((x / 3) * b + b);
            }
        } else {
            System.out.println(a * x);
        }
    }
}