Emma is writing bits (1’s and 0’s) in her notebook. Every second, she writes more bits.
In the 1st second, she writes two bits in her notebook. She starts with 0 and alternates between 0 and 1. They look like this:
0 1
In the 2nd second, she writes three more bits in her notebook. This time, she starts with 1 and keeps alternating between 0 and 1. Now, they look like this:
0 1
1 0 1
After 6 seconds, her notebook looks like this:
0 1
1 0 1
0 1 0 1
1 0 1 0 1
0 1 0 1 0 1
1 0 1 0 1 0 1
If you count carefully, you can see that Emma wrote 15 1's in her notebook after 6 seconds. She wants to know how many 1's she can write in T seconds.
Input Format:
The input contains a single integer T, indicating the time in seconds.
Output Format:
Print the number of 1’s Emma can write in T seconds.
Constraints:
1 ≤ T ≤ 1 000 000 000
