6306: ABC230 —— E - Fraction Floor Sum
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Description
Given is a positive integer $N$. Find the value $\displaystyle\sum_{i=1}^N \left[ \frac{N}{i} \right]$.
Here, for a real number $x, [x]$ denotes the largest integer not exceeding $x$.
Here, for a real number $x, [x]$ denotes the largest integer not exceeding $x$.
Input
Input is given from Standard Input in the following format:
$N$
$N$
Output
Print the answer.
Constraints
$1≤N≤10^{12}$
$N$ is an integer.
$N$ is an integer.
Sample 1 Input
3
Sample 1 Output
5
We have $\left[ \frac{3}{1} \right]+\left[ \frac{3}{2} \right]+\left[ \frac{3}{3} \right]=3+1+1=5$.
Sample 2 Input
10000000000
Sample 2 Output
231802823220