Problems > Sum of Floor Divisions

Sum of Floor Divisions

Difficulty: 1800 4000 ms 128 MB

number-theory

Print ∑i=1..N ⌊N / i⌋.

Input: one integer N.

Output: the sum of floor divisions.

Constraints:

  • 1 ≤ N ≤ 1012

Sample Tests

Input 1
5
Output 1
10
Input 2
1
Output 2
1

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