Vanya got an important task — he should enumerate books in the library and label each book with its number. Each of the *n* books should be assigned with a number from 1 to *n*. Naturally, distinct books should be assigned distinct numbers.

Vanya wants to know how many digits he will have to write down as he labels the books.
The first line contains integer *n* (1 ≤ *n* ≤ 10<sup class="upper-index">9</sup>) — the number of books in the library.
def calculate_nums(self,num):
    num = int(input())
    sum = 0
    for i in range(1, num + 1):
        # 判断i的大小范围，在10^a到10^b之间
        j = 0
        while i >= pow(10, j):
            j += 1
        sum += j
    return sum
	    	 	 		 		   	 	       	 		