#include<cstdio>
#include<fstream>
#include<iostream>
#include<iomanip>
#include<algorithm>
#include<vector>
#include<bitset>
#include<deque>
#include<queue>
#include<set>
#include<map>
#include<cmath>
#include<cstring>
#include<ctime>
#include<cstdlib>
#include<unordered_map>

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<int,int>
#define pll pair<ll,ll>
#define all(x) (x).begin(), (x).end()
#define fi first
#define se second

using namespace std;

const int nmax = 10005;
const int kmax = 305;
const int lmax = 15;

int n, m, k, i, j, x, y, lim, le, ri, mi, l[kmax], r[kmax], ok, ans, sol, a[nmax], b[nmax], lev[nmax], f[lmax][nmax], cost[kmax][kmax];

vector<int> v[nmax], V[nmax];
bitset<nmax> viz;
bitset<kmax> used;

void dfs(int x)
{
    viz[x] = 1;
    for(auto it : v[x])
        if(!viz[it])
        {
            lev[it] = lev[x] + 1;
            f[0][it] = x;
            dfs(it);
        }
}

int LCA(int x, int y)
{
    int lca;

    if(lev[x] > lev[y]) swap(x, y);
    int dif = lev[y] - lev[x];

    for(int i = 0; i <= lim; i++)
        if((1 << i) & dif)
            y = f[i][y];

    if(x == y) lca = x;
    else
    {
        for(int i = lim; i >= 0; i--)
            if(f[i][x] != f[i][y])
            {
                x = f[i][x];
                y = f[i][y];
            }
        lca = f[0][x];
    }

    return lca;
}

int dist(int x, int y)
{
    int lca = LCA(x, y);
    return lev[x] + lev[y] - 2 * lev[lca];
}

bool pairup(int x, int VAL)
{
    if(used[x]) return 0;
    used[x] = 1;

    for(auto it : V[x])
        if(cost[x][it] <= VAL)
            if(!r[it] || pairup(r[it], VAL))
            {
                l[x] = it;
                r[it] = x;
                return 1;
            }

    return 0;
}

int check(int VAL)
{
    memset(l, 0, sizeof(l));
    memset(r, 0, sizeof(r));
    sol = 0;
    for(ok = 1; ok;)
    {
        ok = 0;
        used = 0;
        for(i = 1; i <= k; i++)
            if(!l[i] && pairup(i, VAL))
            {
                sol++;
                ok = 1;
            }
    }

    return sol;
}

int main()
{
    //        freopen("test.in", "r", stdin);
//    freopen("test.out", "w", stdout);

    scanf("%d%d", &n, &k);

    for(i = 1; i <= k; i++)
        scanf("%d", &a[i]);

    for(i = 1; i <= k; i++)
        scanf("%d", &b[i]);

    for(m = n - 1; m; m--)
    {
        scanf("%d%d", &x, &y);
        v[x].pb(y);
        v[y].pb(x);
    }

    dfs(1);

    for(i = 1; (1 << i) <= n; i++)
        for(j = 1; j <= n; j++)
            f[i][j] = f[i - 1][f[i - 1][j]];

    lim = i - 1;

    for(i = 1; i <= k; i++)
        for(j = 1; j <= k; j++)
        {
            V[i].pb(j);
            cost[i][j] = dist(a[i], b[j]);
        }

    le = 0;
    ri = n;
    while(le <= ri)
    {
        int mi = (le + ri) / 2;

        if(check(mi) == k)
        {
            ans = mi;
            ri = mi - 1;
        }
        else le = mi + 1;
    }

    printf("%d\n", ans);

    return 0;
}