AtCoder Regular Contest 090
F
Number of Digits
AtCoder
⌀ 2891
原题
← E→
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Problem Statement

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For a positive integer $n$, let us define $f(n)$ as the number of digits in base $10$.

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You are given an integer $S$. Count the number of the pairs of positive integers $(l, r)$ ($l \leq r$) such that $f(l) + f(l + 1) + ... + f(r) = S$, and find the count modulo $10^9 + 7$.

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Constraints

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  • $1 \leq S \leq 10^8$
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Input

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Input is given from Standard Input in the following format:

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S

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Output

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Print the answer.

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样例

Input #1
1
Output #1
9
There are nine pairs $(l, r)$ that satisfies the condition: $(1, 1)$, $(2, 2)$, $...$, $(9, 9)$.
Input #2
2
Output #2
98
There are $98$ pairs $(l, r)$ that satisfies the condition, such as $(1, 2)$ and $(33, 33)$.
Input #3
123
Output #3
460191684
Input #4
36018
Output #4
966522825
Input #5
1000
Output #5
184984484
题目信息
题号
arc090_d
时间限制
2 s
内存限制
256 MB

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