50A. Domino piling

50A. Domino piling

50A. Domino piling

• time limit per test2 seconds
• memory limit per test256 megabytes
• inputstandard input
• outputstandard output

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:

给你一块M × N个正方形的长方形板。此外，您还可以获得无限数量的标准domino块2 × 1平方米。你可以旋转棋子。您被要求在黑板上放置尽可能多的多米诺骨牌，以满足以下条件：

1. Each domino completely covers two squares.

1. 每个多米诺骨牌完全覆盖两个正方形。

2. No two dominoes overlap.

2. 没有两个多米诺骨牌重叠。

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

3. 每个多米诺骨牌都完全位于董事会内部。允许触摸板的边缘。

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

找出可以放置在这些限制下的多米诺骨牌的最大数量。

Input

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

在一行中，你会得到两个整数M和N——电路板大小的平方（1 ≤ M ≤ N ≤ 16).

Output

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

输出一个数字——可以放置的多米诺骨牌的最大数量。

Examples

input1

2 4

output1

4

input2

3 3

output2

4

Solution

直接m*n/2取商即可

Code

#include <iostream>
using namespace std;

//50A. Domino piling
int main() {
    int m,n = 0;//n：m × n个正方形的长方形板
    cin >> m >> n;
    cout << m * n /2 << endl;
    return 0;
}