21根火柴,人与计算机交换着取,一次取1到4根,但不得不取,谁最后取谁输,编一个C语言程序保证计算机常胜

#include<sio.h>
void main()
{
int a=21,i;
printf("Game begin:\n");
while(a>0)
{
do{
printf("How many stick do you wish to take(1~%d)?",a>4?4:a);
scanf("%d",&i);
}while(i>4||i<1||i>a); /*接收正在确的输入*/
if(a-i>0) printf(" %d stick left in the pile.\n",a-i);
if((a-i)<=0)
{
printf(" You have taken the last stick.\n");
printf(" * * * You lose! \nGame Over.\n"); /*输出取胜标记*/
break;
}
else
printf(" Compute take %d stick.\n",5-i); /*输出计算机取的子数*/
a-=5;
printf(" %d stick left in the pile.\n",a);
}
}