import java.util.Scanner; public class Main{ public static void main(String[] args){ Scanner sc = new Scanner(System.in); long n = sc.nextLong(); for(int i = 1; i <= n; i++){ long a = sc.nextLong(); long b = sc.nextLong(); long c = sc.nextLong(); long d = sc.nextLong(); System.out.println(a * b - c * d); } } }写一个循环来完成这个任务。