Sibling Rivalry

Example

Input

3 3 1 2 4 1 2 2 3 3 1

Output

IMPOSSIBLE

inputFormat

Input

3 3 1 2 4 1 2 2 3 3 1

outputFormat

Output

IMPOSSIBLE

样例

3 3 1 2 4
1 2
2 3
3 1

IMPOSSIBLE