Exhibition

Example

Input

6 5 1 2 3 5 5 5 1 5 5 2 5 4 3 5 3 4 5 2 5 5 1

Output

0.631579

inputFormat

Input

6 5 1 2 3 5 5 5 1 5 5 2 5 4 3 5 3 4 5 2 5 5 1

outputFormat

Output

0.631579

样例

6 5 1 2 3
5 5 5
1 5 5
2 5 4
3 5 3
4 5 2
5 5 1

0.631579