Question
Edward and Maths Competition
Edward participated in one maths competition. He was asked to find the number of ways to choose a pair of an even number and an odd number from the positive integers between 1 and N (inclusive). The order does not matter.
Input
The input line contains only one input N.
Constraints
2≤N≤100
N is an integer.
Constraints
2≤N≤100
N is an integer.
Output
Print the number of ways to choose a pair of an even number and an odd number from the positive integers between 1 and N (inclusive).
Example
Sample Input 1
3
Sample Output 1
2
Sample Input 2
6
Sample Output 2
9
Sample Input 3
11
Sample Output 3
30
3
Sample Output 1
2
Sample Input 2
6
Sample Output 2
9
Sample Input 3
11
Sample Output 3
30