input: Write a python function to find the appropriate index to insert a given element in a sorted sequence.
  assert right_position([1,2,4,5],6)==4
  assert right_position([1,2,4,5],3)==2
  assert right_position([1,2,4,5],7)==4
output: def right_position(arr, target):
      left, right = 0, len(arr)
      while left < right:
          mid = (left + right) // 2
          if arr[mid] < target:
              left = mid + 1
          else:
              right = mid
      return left