After 3 years of university, Beo is still FA. So Beo decide to find a girlfriend before graduation. Beo knew that the first impression was very important. Therefore, Beo wants to have an impressive performance in the first meeting with a beautiful girl. Because of upcoming chirstmas, he want to build a pyramid to replace the Christmas tree:

The top of the pyramid contains one brick.

2nd layer has 1 + 2 = 3 bricks.

3rd layer has 1 + 2 + 3 = 6 bricksh.

….

~n~-th layer has 1 + 2 + … + ~n~ bricks.

Given the number of bricks Beo has, calculate the maximum number of layers Beo can build.

Input

• The first line contains the number n (1 <= n <= 10,000) which is the number of bricks

Output

• The maximum number of layers that can be build

Sample Input:

1

SampleOutput:

 1

Sample Input:

25

Sample Output:

4