We have a tree with N vertices. Vertex 1 is the root of the tree, and the parent of Vertex $i (2 \leq i \leq N)$ is Vertex P_i.

To each vertex in the tree, Snuke will allocate a color, either black or white, and a non-negative integer weight.

Snuke has a favorite integer sequence, X_1, X_2, ..., X_N, so he wants to allocate colors and weights so that the following condition is satisfied for all v.

• The total weight of the vertices with the same color as v among the vertices contained in the subtree whose root is v, is X_v.

Here, the subtree whose root is v is the tree consisting of Vertex v and all of its descendants.

Determine whether it is possible to allocate colors and weights in this way.

Constraints

• $1 \leq N \leq 1 000$
• $1 \leq P_i \leq i - 1$
• $0 \leq X_i \leq 5 000$

Inputs

Input is given from Standard Input in the following format:

N
P_2 P_3 ... P_N
X_1 X_2 ... X_N

Outputs

If it is possible to allocate colors and weights to the vertices so that the condition is satisfied, print POSSIBLE; otherwise, print IMPOSSIBLE.

Examples

Input

3
1 1
4 3 2

Output

POSSIBLE

Input

3
1 2
1 2 3

Output

IMPOSSIBLE

Input

8
1 1 1 3 4 5 5
4 1 6 2 2 1 3 3

Output

POSSIBLE

Input

1

0

Output

POSSIBLE

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