day10:求助！！！

题目：输入两个正整数m和n，求其最大公约数和最小公倍数。

可以正确输出的代码:

#include <stdio.h>

main()

{

int n1,n2,temp,pro,d;

printf("Please enter two number:");

scanf("%d%d",&n1,&n2);

pro = n1 * n2;

if(n1 <= n2)

{

temp = n1;

n1 = n2;

n2 = temp;

}

while(n2 != 0)

{

d = n1 % n2;

n1 = n2;

n2 = d;

}

printf("The divisor is %d,and the muitiple is %d.\n",n1,pro / n1);

return 0;

} 

出错的代码:

#include <stdio.h>

main()

{

int n1,n2,temp,pro,d;

printf("Please enter two number:");

scanf("%d%d",&n1,&n2);

pro = n1 * n2;

if(n1 <= n2)

{

temp = n1;

n1 = n2;

n2 = temp;

}

while(d != 0)

{

d = n1 % n2;

n1 = n2;

n2 = d;

}

printf("The divisor is %d,and the muitiple is %d.\n",n1,pro / n1);

return 0;

} 

思考:为啥第二种代码会出错呢？