시간 제한메모리 제한제출정답맞힌 사람정답 비율
2 초 128 MB73126721536.195%

## 문제

On the first day of Christmas, my true love gave to me, a partridge in a pear tree.

On the second day of Christmas, my true love gave to me, two turtle doves, and a partridge in a pear tree.

OK, now I have 4 birds: two turtle doves and a partridge today, and a partridge from yesterday. My cats are going crazy.

On the third day of Christmas, my true love gave to me, three french hens, two turtle doves, and a partridge in a pear tree.

What's with the birds? I now have ten of them, and no place to put them (except insidethe cats). How long can my true love keep this up?

Given a number of days of Christmas, figure out the total number of gifts I'm going to receive.

## 입력

There will be several test cases in the input. Each test case will consist of a single integer n (1≤n≤1,000,000), on its own line. The input will end with a line with a single 0.

## 출력

For each test case, output a single integer, indicating the number of gifts I’m going to receive, in total. Output no spaces, and do not separate answers with blank lines.

## 예제 입력 1

1
2
3
0


## 예제 출력 1

1
4
10