请问这个代码该怎么改才能当我不想排序的时候可以直接退出，我的代码是按了0之后还会排序一次，再按一次才能退出，我想要让它直接退出.

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAXID 6
#define MAXNAME 8
#define MAXN 100000

struct Student{
    char id[MAXID + 1];
    char name[MAXNAME + 1];
    int grade;
}Record[MAXN];

int CompareId(const void *a, const void *b)
{
    return strcmp(((const struct Student *)a)->id, ((const struct Student *)b)->id);
}

int CompareName(const void *a, const void *b)
{
    int k = strcmp(((const struct Student *)a)->name,((const struct Student *)b)->name);
    if (!k)
        strcmp(((const struct Student *)a)->id, ((const struct Student *)b)->id);
    return k;
}

int CompareGrade(const void *a, const void *b)
{
    int k = (((const struct Student *)a)->grade>((const struct Student *)b)->grade)?1:0;
    if (!k){
        k = (((const struct Student *)a)->grade<((const struct Student *)b)->grade) ? -1 : 0;
        if (!k)
            strcmp(((const struct Student *)a)->id, ((const struct Student *)b)->id);
    }
    return k;
}

int main()
{
    int N, C, i;
    printf("请输入记录的条数：\n");
    scanf("%d", &N);
    printf("请输入学生记录（格式为：学号 姓名 成绩）：\n");
    for (i = 0; i < N; i++)
    {
        scanf("%s %s %d",&Record[i].id,&Record[i].name,&Record[i].grade);
    }   
    while(C!=0);
    {
        printf("请输入指定排序的列号：\n");
        scanf("%d",&C);
    switch (C)
    {
    case 1:qsort(Record, N, sizeof(struct Student), CompareId);
        break;
    case 2:qsort(Record, N, sizeof(struct Student), CompareName);
        break;
    case 3:qsort(Record, N, sizeof(struct Student), CompareGrade);
        break;
    }
    printf("排序后的结果为：\n");
    for (i = 0; i < N; i++)
        printf("%s %s %d\n", Record[i].id, Record[i].name, Record[i].grade);
    }
    return 0;
}

卡住可能是你的学号不是六位