Problem:
Score : 300 points

Problem Statement

There are N integers, A_1, A_2, ..., A_N, written on the blackboard.

You will choose one of them and replace it with an integer of your choice between 1 and 10^9 (inclusive), possibly the same as the integer originally written.

Find the maximum possible greatest common divisor of the N integers on the blackboard after your move.

Constraints

All values in input are integers.

2 \leq N \leq 10^5

1 \leq A_i \leq 10^9

Output

Input is given from Standard Input in the following format:

N
A_1 A_2 ... A_N

Output

Print the maximum possible greatest common divisor of the N integers on the blackboard after your move.

Sample Input 1

3
7 6 8

Sample Output 1

2

If we replace 7 with 4, the greatest common divisor of the three integers on the blackboard will be 2, which is the maximum possible value.

Sample Input 2

3
12 15 18

Sample Output 2

6

Sample Input 3

2
1000000000 1000000000

Sample Output 3

1000000000

We can replace an integer with itself.

Solution in Go (1.6) (judge verdict: Accepted)

package main

import "fmt"

func gcd(a, b int) int {
	if b == 0 {
		return a
	}
	return gcd(b, a%b)
}

func main() {
	var n int
	fmt.Scan(&n)
	a := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Scan(&a[i])
	}

	l := make([]int, n+1)
	r := make([]int, n+1)
	l[0] = 0
	r[0] = 0
	for i := 0; i < n; i++ {
		l[i+1] = gcd(a[i], l[i])
		r[n-1-i] = gcd(a[n-1-i], r[n-i])
	}

	ans := 0
	for i := 0; i < n; i++ {
		t := gcd(l[i], r[i+1])
		if ans < t {
			ans = t
		}
	}

	fmt.Println(ans)
}