OneForYou | Topcoder Archive

Problem Statement

When trying to divide coins "equally" between two people, an old gag goes something like this...

The person dividing up the loot says "One for you, and one for me" giving one coin to the other person and then themselves.
Next they say "And that's two for you", while giving the other person a second coin.
Then, they say "And that's one, two, for me", giving themselves two coins, additional to the first one they already had.
Then, they say "That's three for you, and one, two, three, for me", given the other person a third coin before giving themselves three more coins.
... and so on

The are N coins to be divided. Assuming they are divided in this sneaky fashion, how many coins will the first person end up getting?

Definition

Class:: OneForYou
Method:: coinCount
Parameters:: long
Returns:: long
Method signature:: long coinCount(long N)
(be sure your method is public)

Constraints

N will be between 0 and 10^15, inclusive.

Examples

```
2
```
```
Returns: 1
```
In this case, it's actually fair, each person gets one coin.
```
9
```
```
Returns: 6
```
This is three full rounds of dividing coins.
```
11
```
```
Returns: 7
```
Here we run out of coins before the person dividing the coins takes four of them, so he takes as many as he can.
```
33
```
```
Returns: 26
```

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