题目描述
Problem Statement
You are given an integer sequence $A=(A_1,A_2,\cdots,A_N)$ of length N, and another integer sequence $P=(P_2,\cdots,P_N)$ of length N-1. Note that the index of P starts at 2. It is guaranteed that $1 \leq P_i < i$ for each i.
You will now repeat the following operation 10^{100} times.
- For each $i=2,\cdots,N$, in this order, replace the value of A_{P_i} with A_{P_i}+A_{i}.
Determine whether A_1 will be positive, negative, or zero when all operations are completed.
Input
The input is given from Standard Input in the following format:
N
$A_1 A_2 \cdots A_N$
$P_2 \cdots P_N$
Output
If A_1 is positive when all operations are completed, print +; if it is negative, print -; if it is zero, print 0.
Constraints
- $2 \leq N \leq 250000$
- -$10^9 \leq A_i \leq 10^9$
- $1 \leq P_i < i$
- All input values are integers.
Sample Input 1
4
1 -2 3 -4
1 2 3
Sample Output 1
-
Shown below are the results of the first few operations.
- After the first operation:
- Before the operation: A=(1,-2,3,-4).
- Processing for i=2: Replace the value of A_1 with A_1+A_2=1+(-2)=-1.
- Processing for i=3: Replace the value of A_2 with A_2+A_3=-2+3=1.
- Processing for i=4: Replace the value of A_3 with A_3+A_4=3+(-4)=-1.
-
After the operation: A=(-1,1,-1,-4).
-
After the second operation, A=(0,0,-5,-4).
- After the third operation, A=(0,-5,-9,-4).
- After the fourth operation, A=(-5,-14,-13,-4).
- $\vdots$
After 10^{100} operations, A_1 will be negative.
Thus, you should print -.
Sample Input 2
3
0 1 -1
1 1
Sample Output 2
0
Sample Input 3
5
1 -1 1 -1 1
1 1 2 2
Sample Output 3
+
Sample Input 4
20
568273618 939017124 -32990462 -906026662 403558381 -811698210 56805591 0 436005733 -303345804 96409976 179069924 0 0 0 -626752087 569946496 0 0 0
1 1 1 4 4 6 7 2 2 3 3 8 13 14 9 9 15 18 19
Sample Output 4
+
输入格式
见题面 Input 部分
输出格式
见题面 Output 部分