用C语言写以下程序：输入一个整数，输出每个数字对应的拼音。当整数为负数时，先输出fu字。

#include <stdio.h>

int main()
{
    int num;
    scanf("%d", &num);  // 输入整数
    if(num < 0)  // 判断是否为负数
    {
        printf("fu ");  // 输出fu字
        num = -num;  // 负数转为正数
    }
    // 数字对应拼音
    switch(num / 1000)
    {
        case 1: printf("yi "); break;
        case 2: printf("er "); break;
        case 3: printf("san "); break;
        case 4: printf("si "); break;
        case 5: printf("wu "); break;
        case 6: printf("liu "); break;
        case 7: printf("qi "); break;
        case 8: printf("ba "); break;
        case 9: printf("jiu "); break;
    }
    switch(num / 100 % 10)
    {
        case 1: printf("yi "); break;
        case 2: printf("er "); break;
        case 3: printf("san "); break;
        case 4: printf("si "); break;
        case 5: printf("wu "); break;
        case 6: printf("liu "); break;
        case 7: printf("qi "); break;
        case 8: printf("ba "); break;
        case 9: printf("jiu "); break;
    }
    switch(num / 10 % 10)
    {
        case 1: printf("yi "); break;
        case 2: printf("er "); break;
        case 3: printf("san "); break;
        case 4: printf("si "); break;
        case 5: printf("wu "); break;
        case 6: printf("liu "); break;
        case 7: printf("qi "); break;
        case 8: printf("ba "); break;
        case 9: printf("jiu "); break;
    }
    switch(num % 10)
    {
        case 1: printf("yi "); break;
        case 2: printf("er "); break;
        case 3: printf("san "); break;
        case 4: printf("si "); break;
        case 5: printf("wu "); break;
        case 6: printf("liu "); break;
        case 7: printf("qi "); break;
        case 8: printf("ba "); break;
        case 9: printf("jiu "); break;
    }
    return 0;
}