codeforces#P1985G. D-Function
D-Function
Description
Let $D(n)$ represent the sum of digits of $n$. For how many integers $n$ where $10^{l} \leq n < 10^{r}$ satisfy $D(k \cdot n) = k \cdot D(n)$? Output the answer modulo $10^9+7$.
The first line contains an integer $t$ ($1 \leq t \leq 10^4$) – the number of test cases.
Each test case contains three integers $l$, $r$, and $k$ ($0 \leq l < r \leq 10^9$, $1 \leq k \leq 10^9$).
For each test case, output an integer, the answer, modulo $10^9 + 7$.
Input
The first line contains an integer $t$ ($1 \leq t \leq 10^4$) – the number of test cases.
Each test case contains three integers $l$, $r$, and $k$ ($0 \leq l < r \leq 10^9$, $1 \leq k \leq 10^9$).
Output
For each test case, output an integer, the answer, modulo $10^9 + 7$.
6
0 1 4
0 2 7
1 2 1
1 2 3
582 74663 3
0 3 1
2
3
90
12
974995667
999
Note
For the first test case, the only values of $n$ that satisfy the condition are $1$ and $2$.
For the second test case, the only values of $n$ that satisfy the condition are $1$, $10$, and $11$.
For the third test case, all values of $n$ between $10$ inclusive and $100$ exclusive satisfy the condition.