package main

import "strconv"

type LCPTrieNode struct {
	children [10]*LCPTrieNode
	has      [2]bool
}

func longestCommonPrefix(arr1 []int, arr2 []int) int {
	update := func(node *LCPTrieNode, number string, index int) int {
		best := 0
		for i := range number {
			child := number[i] - '0'
			if node.children[child] == nil {
				node.children[child] = &LCPTrieNode{}
			}
			node = node.children[child]
			node.has[index] = true

			if node.has[index] && node.has[(index+1)%2] {
				best = i + 1
			}
		}

		return best
	}

	root := LCPTrieNode{}
	for _, num := range arr1 {
		strnum := strconv.Itoa(num)
		update(&root, strnum, 0)
	}

	longest := 0
	for _, num := range arr2 {
		strnum := strconv.Itoa(num)
		longest = max(longest, update(&root, strnum, 1))
	}

	return longest
}