import math

def bsearch(A, key_to_search):
    n = len(A)
    lg = int(math.log2(n-1)) + 1
    pos = 0
    for i in range(lg - 1, -1, -1):
        if A[pos] == key_to_search:
            return pos
        new_pos = pos | (1 << i)
        if new_pos < n and A[new_pos] <= key_to_search:
            pos = new_pos
    return pos if A[pos] == key_to_search else -1

if __name__ == "__main__":
    A = list(map(int, input("Enter the array elements: ").split()))
    key = int(input("Enter the number to search: "))
    print(bsearch(A, key))