Cho max = 99 -> 10000000000?

Đây là code C :

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
void Sosanh (int soHientai) ;
int taoSobimat(int MAX);
int main(int argc, char *argv[])
{
int soBimat,soHientai, che_do_nguoi_choi,gioi_han_bang_so,MAX   = 0;/* i, b,*/
printf("===== Welcome ban toi voi chuong trinh : =====
");
printf("======== Lon hon!Nho hon! Chuc mung ! ========

");
printf("Phan thiet lap : 

");
printf("Che do :
");
printf("1. 1 nguoi choi   2. 2 nguoi choi 

");
scanf("%d",&che_do_nguoi_choi);
printf("Cap do (gioi han) choi: 

");
printf("1. 100
");
printf("2. 200
");
printf("3. 300
");
scanf("%d",&gioi_han_bang_so);
switch(gioi_han_bang_so)
{
case 1 :
    MAX = 99;
case 2 :
    MAX = 199;
case 3 :
    MAX = 299;
}
soBimat = taoSobimat(MAX);
Sosanh(soBimat);
}
int taoSobimat(int MAX)
{
const int MIN =0;
int socan=0;
srand(time(NULL));
socan = (rand()%(MAX - MIN +1))+MIN;
return taoSobimat;
}
void Sosanh(int soBimat )
{
int soHientai,as = 0;
do
{
int i = 0;
do
{
printf("Moi ban nhap so :
");
scanf("%d",&soHientai);
if (soHientai > soBimat)
{
    printf("Nho hon !
");
    i++;
}
else if (soHientai < soBimat)
{
    printf("Lon hon !
");
    i++;
}
else
{
    printf("Chuc mung ban da tim ra so bi mat la : %d trong %d lan doan ! 

",soBimat,i);
    printf("Ban co muon choi tiep ?
");
    printf("1. Co         2. Khong
");
    scanf("%d",&as);
}
}while (soHientai!=soBimat);
}while (as != 2);
}

lúc cho MAX = 99 thì nó phan lên < 1000000 wtf??