binary search

n = int(input())
line = list(map(int, input().split(" ")))
number_to_find = int(input())
left = 0
right = n - 1
flag = 0
while left <= right:
    mid = (left + right) // 2
    if line[mid] == number_to_find:
        flag = 1
        break
    elif line[mid] > number_to_find:
        right = mid - 1
    elif line[mid] < number_to_find:
        left = mid + 1
if flag == 1:
    print('number found')
else:
    print('not found')