c语言程序这个怎么弄

试一下这个
#include<stdio.h>
int main(void)
{
int a,b,x,sum;
printf("[1] Add\n[2] Subtract\n[3] Multiply\n[4] Divide\n");
printf("Enter your choice: ");
scanf("%d",&x);
printf("first num: ");
scanf("%d",&a);
printf("second num: ");
scanf("%d",&b);
switch(x)
{
case 1:
sum = a+b;
printf("%d + %d = %d\n",a,b,sum);
break;
case 2:
sum = a-b;
printf("%d - %d = %d\n",a,b,sum);
break;
case 3:
sum = a*b;
printf("%d * %d = %d\n",a,b,sum);
break;
case 4:
sum = a/b;
printf("%d / %d = %d\n",a,b,sum);
break;
default:
printf("input error\n");
break;
}
return 0;
}