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The area of a right triangle

#### Problem

Given the lengths of the two legs in a right triangle and output its area.

The area of a right triangle formula is

\(S = {1 \over 2} \cdot a \cdot b\),

`a, b`

- length of legs.

**Input format**
Given two real numbers – length of legs (

`a, b`

), each on a separate line (1 <= a, b <= 10

^{4}).

**Output format**
Output one number - the area of a right triangle with an accuracy of at least three decimal places.

###### Examples

N |
Input |
Output |

1 |
2.0
3.0 |
3.000 |

2 |
26.0
78.0 |
1014.000 |

3 |
3.5
7.8 |
13.650 |