这个程序问题在哪，大一新生求帮忙？
#include<stdio.h>
#define j 15
int main()
{
int b,n,m,k,i,a[j],x,top,bot,mid,find=0;
printf("please enter fifteen numbers:\n");
for(i=0;i<j;i++)
scanf("%d",&a[i]);
for(b=0;b<j-1;b++)
{
k=b;
for(n=b+1;n<j;n++)
if(a[n]>a[k])
k=n;
if(k!=n)
{
m=a[b];a[b]=a[k];a[k]=m;
}

}
for(i=0;i<j;i++)
printf("%d ",a[i]);
printf("please enter find num:\n");
scanf("%d",&x);
top=0;bot=j-1;
while(top<=bot&&find==0)
{
mid=(top+bot)/2;
if(x==a[mid])
find=1;
else if(x<a[mid])
bot=mid-1;
else top=mid+1;
}
if(find==0) printf("%d is not found",x);
else printf("%d is a[%d]",x,mid);
return 0;
}