输出ab之间的回文数，为什么不能循环
#include<math.h>
#include<stdio.h>
main()
{
    long a,b,n=0,k;
    do
    {
        printf("please input a b(5 <= a < b <= 1000,000,000)");
        scanf("%ld%ld",&a,&b);
    }
    while(a<5||b>1000000000||b<=a);
    for (; a<=b; a=a+1)
    {
        k=a;
        do
        {
            n=n*10+k%10;
            k=k/10;
        }
        while(k!=0);
        if (n==a)
        {
            printf("%ld\n",a);
        }
    }
}

do
        {
            n=n*10+k%10;
            k=k/10;
        }
        while(k!=0);
这端是把数逆序输出，之后在判断回文数