#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;

const int N = 2e5 + 10;
vector<int> GN[N], GM[N];
int a[N], b[N];
int ans;
int n, m;

void dfs(int pN, int faN, int pM, int faM, int dep)
{
    ans = max(ans, dep);
    map<int, int> bk;
    for (auto sonN : GN[pN])
        if (sonN != faN) 
            bk[a[sonN]] = sonN;

    for (auto sonM : GM[pM])
    {
        if (sonM != faM)
            if (bk.count(b[sonM]))
            {
                dfs(bk[b[sonM]], pN, sonM, pM, dep + 1);
            }
    }
}

int main()
{
    int x, y;
    cin >> n >> m;
    for (int i = 1; i <= n; i++) cin >> a[i];
    for (int i = 1; i <= m; i++) cin >> b[i];

    for (int i = 1; i < n; i++)  
    {
        cin >> x >> y;
        GN[x].push_back(y);
        GN[y].push_back(x);
    }
    for (int i = 1; i < m; i++)  
    {
        cin >> x >> y;
        GM[x].push_back(y);
        GM[y].push_back(x);
    }

    dfs(1, 0, 1, 0, 1);  
    cout << ans << endl;

    return 0;
}