Byteland 航空公司最近为其机队增加了一款新机型。该机型商务舱有 $n_{1}$ 排座位，经济舱有 $n_{2}$ 排座位。商务舱每排有 $k_{1}$ 个座位，经济舱每排有 $k_{2}$ 个座位。
请编写一个程序，完成以下任务：
标准输入的唯一一行包含四个整数 $n_{1}$、$k_{1}$、$n_{2}$ 和 $k_{2}$（$1 \le n_{1}, k_{1}, n_{2}, k_{2} \le 1\,000$），以空格分隔。
标准输出的唯一一行应包含一个整数，即飞机上可用座位的总数。
2 5 3 20
70
The discussion section is only for posting: General Discussions (problem-solving strategies, alternative approaches), and Off-topic conversations.
This is NOT for reporting issues! If you want to report bugs or errors, please use the Issues section below.
If you find any issues with the problem (statement, scoring, time/memory limits, test cases, etc.), you may submit an issue here. A problem moderator will review your issue.
Guidelines: