#include<stdio.h>
#include<stdlib.h>
int a[]={10,22,42,51,56,63,78,99,102,118};
int binSearch(int* a, int begin, int end, int k){
int mid = begin + ( (end - begin)>>1 ),index;
index = a[mid] < k && begin + 1 < end ? binSearch(a,mid+1,end,k) :
( a[mid] > k && begin + 1 < end ? binSearch(a,begin,mid,k) :
mid * (a[mid] == k) + (a[mid] != k)*(-1));
return index;
}
int main() {
int result = binSearch(a,0, sizeof(a)/sizeof(int), 22);
printf("%d
",result);
return 0;
}