def sequential_search(n, target, array):
  for i in range(n):
    if array[i] == target:
      return i+1

#이진 탐색 소스코드 구현(재귀 함수)
def binary_search(array, target, start, end):
  if start > end:
    return None
  mid = (start + end) // 2
  if array[mid] == target:
    return mid
  elif array[mid] > target:
    return binary_search(array, target, start, mid-1)
  else:
    return binary_search(array, target, mid+1, end)

#이진 탐색 소스코드(반복문)
def binary_search(array, target, start, end):
  while start <= end:
    mid= (start+end) //2
    if array[mid] == target:
      return mid
    elif array[mid] > target:
      end = mid+1
    else:
      start = mid+1
  return None

inport sys
input_data = sys.stdin.readline().rstrip()