#include<stdio.h>

int binarysearch(int [], int, int, int, int);

void main()
 {
   const int arraysize = 7;
   int a[arraysize], key, result;
	for(int i=0; i<arraysize; i++)
		a[i]  = 2*i;
	printf("Enter a number between 0 and 12	: \t");
	scanf("%d", &key);
	result = binarysearch(a, key, 0, arraysize-1, arraysize);

		if(result !=-1)
		printf("\n %d found at array element %d", key, result);
		else
		printf("\n %d not found", key);

 }


 int binarysearch(int b[], int searchkey, int low, int high, int size)
 {
 int middle;
	while(low<=high)
	 {
	   middle = (low + high)/2;
		if (searchkey == b[middle])
			return middle;
		else if(searchkey < b[middle])
			high = middle-1;
		     else
			low = middle +1;
	  }
     return -1;
 }