All positive integers from to are written consecutively from left to right: .
How many ways are there to cross out all the digits of the obtained number, except four, so that the remaining digits form the number without rearrangement?
For example, for from the number , you can obtain only in one way:
1 34567891 0 111 2 131 4 151617181920
One positive integer .
Print the number of possible ways to obtain the number .