用二分法找数

#include<stdio.h>
int main()
{
int a[15]={1,2,3,4,5,6,7,8,9,10,11,12,13,14,15};
int i,n,low,high,mid,flag;
while(scanf("%d",&n)!=EOF)
{
flag=-1;
low=0;
high=14;
while(low<high)
{
mid=(low+high)/2;
if(n>a[mid])
low=mid+1;
else if(n<a[mid])
high=mid;
else
{
flag=mid;
break;
}
}
printf("%d\n",flag+1);
}
return 0;
}