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50A. Domino piling ​

greedy/math, 800, http://codeforces.com/problemset/problem/50/A

You are given a rectangular board of M × N squares. Also you are given an unlimited number of standard domino pieces of 2 × 1 squares. You are allowed to rotate the pieces. You are asked to place as many dominoes as possible on the board so as to meet the following conditions:

  1. Each domino completely covers two squares.

  2. No two dominoes overlap.

  3. Each domino lies entirely inside the board. It is allowed to touch the edges of the board.

Find the maximum number of dominoes, which can be placed under these restrictions.

Input

In a single line you are given two integers M and N — board sizes in squares (1 ≤ M ≤ N ≤ 16).

Output

Output one number — the maximal number of dominoes, which can be placed.

Examples

input

2 4

output

4

input

3 3

output

4

2022fall-cs101，杨文可，哲学系。

首先竖着铺。如果n是偶数，就完成了。如果n是奇数，再在剩下来的一行里面横着铺。

python
m, n = map(int, input().split())  
 
num = n // 2 * m  
if n % 2 != 0:  
    num += m // 2  
 
print(num)

不同 于 Theatre Square，多米诺骨牌可以横放或竖放，可以不铺满（其实最多空一格）可直接按面积相除取整

python
M, N = [int(x) for x in input().split()] 
print(int(M*N/2))

short code

python
print(eval('*'.join(input().split()))//2)

eval会把字符 串当成算式计算也可返回相应的 list,tuple等