Codeforces Round 146 (Div. 1)
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Let's denote $*d*(*n*)$ as the number of divisors of a positive integer $*n*$. You are given three integers $*a*$, $*b*$ and $*c*$. Your task is to calculate the following sum:
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Find the sum modulo $1073741824$ $(2^{30})$.
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Input
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The first line contains three space-separated integers $*a*$, $*b*$ and $*c*$ ($1 ≤ *a*, *b*, *c* ≤ 2000$).
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Output
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Print a single integer — the required sum modulo $1073741824$ $(2^{30})$.
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Note
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For the first example.
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$*d*(1·1·1) = *d*(1) = 1$;$*d*(1·1·2) = *d*(2) = 2$;$*d*(1·2·1) = *d*(2) = 2$;$*d*(1·2·2) = *d*(4) = 3$;$*d*(2·1·1) = *d*(2) = 2$;$*d*(2·1·2) = *d*(4) = 3$;$*d*(2·2·1) = *d*(4) = 3$;$*d*(2·2·2) = *d*(8) = 4$.
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So the result is $1 + 2 + 2 + 3 + 2 + 3 + 3 + 4 = 20$.
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样例
Input #1
2 2 2
Output #1
20
InputCopy
OutputCopy
Input #2
4 4 4
Output #2
328
InputCopy
OutputCopy
Input #3
10 10 10
Output #3
11536
InputCopy
OutputCopy
题目信息
标签
组合数学
动态规划
模拟
数学
数论
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