Problems
Simple Addition
Simple Addition
Let's define the next recursive function $F(n)$, where
$$
F(n) = \begin{cases}
n~\%~10,~n~\%~10 > 0 \\
0, n = 0\\
F(n / 10), otherwise
\end{cases}
$$
Let's define the function $S(p, q)$ as follows:
$$
S(p, q) = \sum_{i=p}^{q} F(i)
$$
In this problem you have to calculate $S(p, q)$ on given values of $p$ and $q$.
\InputFile
Consists of multiple test cases. Each line contains two nonnegative integers $p$ and $q~(p \le q)$. $p$ and $q$ will fit in $32$ bit signed integer. Input is terminated by a line with two negative integers. This line should not be processed.
\OutputFile
For each pair $p$ and $q$ print the value $S(p, q)$ on a single line.
Input example #1
1 10 10 20 30 40 -1 -1
Output example #1
46 48 52