}
public static void chengfa()
{
Random ran=new Random();
Scanner sc=new Scanner(System.in);
//System.out.print("请输入两个一位的正整数");
int a=ran.nextInt(10);
int b=ran.nextInt(10);
System.out.println("a="+a);
System.out.println("b="+b);
System.out.println("第一题");
System.out.println("How much is 6 times 7 ?");
int x=sc.nextInt();
while (true)
{