Undiv2 | Topcoder Archive

Problem Statement

Given a positive integer x, let s(x) be the second smallest positive integer that does not divide x.

For example, let x = 6. The integers that do not divide x are 4, 5, 7, 8, 9, 10, ... The second smallest of these is 5. Hence we have s(6) = 5.

Hero took a blank sheet of paper. For each i between 1 and n, inclusive, he computed the value s(i) and wrote it on the paper. You are given the int n. Compute and return the sum of the n numbers on Hero's paper.

Definition

Class:: Undiv2
Method:: getsum
Parameters:: int
Returns:: long
Method signature:: long getsum(int n)
(be sure your method is public)

Constraints

n will be between 1 and 1,000,000,000, inclusive.

Examples

```
1
```
```
Returns: 3
```
The smallest two positive integers that don't divide 1 are 2 and 3. Thus, we have s(1) = 3.
```
2
```
```
Returns: 7
```
```
3
```
```
Returns: 11
```
The answer is s(1) + s(2) + s(3) = 3 + 4 + 4 = 11.
```
5
```
```
Returns: 19
```
```
8
```
```
Returns: 32
```
```
13
```
```
Returns: 53
```

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