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

using namespace std;

#define dbg(x) (cout<<#x<<" = "<<(x)<<'\n')
#ifdef HOME
const string inputFile = "input.txt";
const string outputFile = "output.txt";
#else
const string problemName = "";
const string inputFile = problemName + ".in";
const string outputFile = problemName + ".out";
#endif

typedef long long int lld;
typedef pair<int, int> PII;
typedef pair<int, lld> PIL;
typedef pair<lld, int> PLI;
typedef pair<lld, lld> PLL;

const int INF = (1LL << 31) - 1;
const lld LINF = (1LL << 62) - 1;
const int dx[] = {1, 0, -1, 0, 1, -1, 1, -1};
const int dy[] = {0, 1, 0, -1, 1, -1, -1, 1};
const int MOD = (int)(1e9) + 7;

const int NMAX = 10000 + 5;
const int KMAX = 300 + 5;

int N, K, sol;
vector<int> V[NMAX];
PII RMQ[16][2 * NMAX];
int euler[2 * NMAX], cnt;
int first[NMAX];
int lvl[NMAX];
int dad[NMAX];
int A[NMAX];
int B[NMAX];
int VAL;
vector<PII> AA[NMAX];
bitset<NMAX> viz;
int P[NMAX];
int Q[NMAX];

void dfs(int x) {
    euler[++cnt] = x;
    first[x] = cnt;

    for(auto y : V[x]) {
        if(y == dad[x])
            continue;
        lvl[y] = lvl[x] + 1;
        dad[y] = x;
        dfs(y);
        euler[++cnt] = x;
    }
}

void build() {
    int i, j, p;

    for(i = 1; i <= cnt; i++)
        RMQ[0][i] = make_pair(lvl[euler[i]], euler[i]);

    for(i = 1, p = 2; 1 + p / 2 <= cnt; i++, p *= 2)
        for(j = 1; j + p / 2 <= cnt; j++)
            RMQ[i][j] = min(RMQ[i - 1][j], RMQ[i - 1][j + p / 2]);
}

int query(int x, int y) {
    int d = y - x + 1;
    int i = log2(d + 0.5);
    int p = (1 << i);

    return min(RMQ[i][x], RMQ[i][y - p + 1]).second;
}

int lca(int x, int y) {
    x = first[x];
    y = first[y];
    if(x > y)
        swap(x, y);
    return query(x, y);
}

int pair_up(int x) {
    if(viz[x])
        return 0;

    viz[x] = 1;

    for(auto y : AA[x]) {
        if(y.second <= VAL) {
            if((!Q[y.first]) || (pair_up(Q[y.first]))) {
                P[x] = y.first;
                Q[y.first] = x;
                return 1;
            }
        }
    }

    return 0;
}

int main() {
    int i, j, x, y, z;

    freopen(inputFile.c_str(), "r", stdin);
    freopen(outputFile.c_str(), "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(i = 2; i <= N; i++) {
        scanf("%d%d", &x, &y);
        V[x].push_back(y);
        V[y].push_back(x);
    }

    dfs(1);

    build();

    for(i = 1; i <= K; i++)
        for(j = 1; j <= K; j++) {
            x = A[i];
            y = B[j];
            z = lca(x, y);
            AA[i].push_back(make_pair(j, lvl[x] + lvl[y] - 2 * lvl[z]));
        }

    int lo = 0;
    int hi = NMAX;
    int ans, ok;

    sol = NMAX;

    while(lo <= hi) {
        VAL = (lo + hi) / 2;

        ans = 0;
        memset(P, 0, sizeof(P));
        memset(Q, 0, sizeof(Q));

        do {
            ok = 0;
            viz = 0;

            for(i = 1; i <= K; i++)
                if(!P[i])
                    ok |= pair_up(i);

        } while(ok);

        for(i = 1; i <= K; i++)
            if(P[i])
                ans++;

        if(ans == K) {
            hi = VAL - 1;
            sol = VAL;
        } else
            lo = VAL + 1;
    }

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

    return 0;
}