#include <stdio.h>


/*
 * return the index of number x in array a or -1 if not found.
 * Array a must be sorted.
 */
int search(int x, int size, int *a)
{
    if (size > 0) {
        int mid = size / 2;
        if (a[mid] == x)
            return mid;
        else if (a[mid] > x)
	    return search(x, mid, a);
        else {
	    int subsearch = search(x, size - (mid + 1), a + mid + 1);
	    if (subsearch == -1)
		return subsearch;
	    else
		return subsearch + mid + 1;
	}
    }
    return -1;
}


int main()
{
    int i, a[10], x;

    for (i = 0; i < 10; i++)
        scanf("%d", &a[i]);

    while (printf("Search for: "), scanf("%d", &x) == 1)
        printf("search for %d yields %d\n", x, search(x, 10, a));

    return 0;
}