弱弱的C语言问题

int binsearch(long a[],int m,long x)
{
int low,high,mid;
low=0;
high=n-1;
while(low<=high)
{
mid=(high+low)/2;
if(x>a[mid]) low=mid+1;
else if(x<a[mid]) high=mid-1;
else return (mid);
}
return(-1);
}
main()
{
int binsearch(long a[],int m,long x);
float score[40];
int n,i,pos;
long num[40],x;
printf("Please enter the total number:");
scanf("%d",&n);
printf ("Please enter the number and score:\n");
for(i=0;i<n;i++)
scanf("%Ld%f",&num[i],&score[i]);
printf("please enter the searching number:\n");
scanf("%Ld",&x);
pos=binsearch(num,n,x);
if(pos!=-1)
printf("score=%4.0\n",score[pos]);
else
printf("not found!\n");
}
应该没打错，要求是二分法查找成绩，把书上的程序copy了一下，但是输入以后总是显示“not found”
不知道为什么。。。TC环境。