Problem:
Score : 400 points

Problem Statement

Mountaineers Mr. Takahashi and Mr. Aoki recently trekked across a certain famous mountain range.
The mountain range consists of N mountains, extending from west to east in a straight line as Mt. 1, Mt. 2, ..., Mt. N.
Mr. Takahashi traversed the range from the west and Mr. Aoki from the east.

The height of Mt. i is h_i, but they have forgotten the value of each h_i.
Instead, for each i (1 ≤ i ≤ N), they recorded the maximum height of the mountains climbed up to the time they reached the peak of Mt. i (including Mt. i).
Mr. Takahashi's record is T_i and Mr. Aoki's record is A_i.

We know that the height of each mountain h_i is a positive integer.
Compute the number of the possible sequences of the mountains' heights, modulo 10^9 + 7.

Note that the records may be incorrect and thus there may be no possible sequence of the mountains' heights.
In such a case, output 0.

Constraints

1 ≤ N ≤ 10^5

1 ≤ T_i ≤ 10^9

1 ≤ A_i ≤ 10^9

T_i ≤ T_{i+1} (1 ≤ i ≤ N - 1)

A_i ≥ A_{i+1} (1 ≤ i ≤ N - 1)

Input

The input is given from Standard Input in the following format:

N
T_1 T_2 ... T_N
A_1 A_2 ... A_N

Output

Print the number of possible sequences of the mountains' heights, modulo 10^9 + 7.

Sample Input 1

5
1 3 3 3 3
3 3 2 2 2

Sample Output 1

4

The possible sequences of the mountains' heights are:

1, 3, 2, 2, 2

1, 3, 2, 1, 2

1, 3, 1, 2, 2

1, 3, 1, 1, 2

for a total of four sequences.

Sample Input 2

5
1 1 1 2 2
3 2 1 1 1

Sample Output 2

0

The records are contradictory, since Mr. Takahashi recorded 2 as the highest peak after climbing all the mountains but Mr. Aoki recorded 3.

Sample Input 3

10
1 3776 3776 8848 8848 8848 8848 8848 8848 8848
8848 8848 8848 8848 8848 8848 8848 8848 3776 5

Sample Output 3

884111967

Don't forget to compute the number modulo 10^9 + 7.

Sample Input 4

1
17
17

Sample Output 4

1

Some mountain ranges consist of only one mountain.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;

public class Main {
	final static long MOD = 1000000007;

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		long[] T = new long[N];
		long[] A = new long[N];
		for (int i=0; i<N; i++) T[i] = sc.nextLong();
		for (int i=0; i<N; i++) A[i] = sc.nextLong();
		//
		long[] B = new long[N];
		for (int i=0; i<N; i++) B[i] = min(T[i], A[i]);
		long ans = 0;
		if (max(T)==max(A) && max(T)==max(B)) {
			ans = 1;
			int top = indexOf(B, max(B));
			for (int i=1; i<=top; i++) {
				if (B[i-1]!=B[i]) continue;
				ans *= B[i];
				if (ans>MOD) ans %= MOD;
			}
			for (int i=B.length-2; i>top; i--) {
				if (B[i+1]!=B[i]) continue;
				ans *= B[i];
				if (ans>MOD) ans %= MOD;
			}
		}
		//
		System.out.println(ans);
		sc.close();
	}
	
	static long min(long a, long b) {
		return a<b ? a:b;
	}
	
	static long max(long[] array) {
		long max = Long.MIN_VALUE;
		for (int i=0; i<array.length; i++) {
			if (array[i]>max) max = array[i];
		}
		return max;
	}
	
	static int indexOf(long[] a, long m) {
		for (int i=0; i<a.length; i++) {
			if (a[i]==m) return i;
		}
		return -1;
	}
}