mod = 1000000007
eps = 10**-9


def main():
    import sys
    from collections import deque
    input = sys.stdin.buffer.readline

    N, M = map(int, input().split())
    A = list(map(int, input().split()))
    adj = [[] for _ in range(N+1)]
    for _ in range(N-1):
        a, b = map(int, input().split())
        adj[a].append(b)
        adj[b].append(a)

    def mex(dic):
        for i in range(N+1):
            if i not in dic:
                return i
            else:
                if dic[i] == 0:
                    return i

    que = deque()
    que.append(1)
    seen = [-1] * (N+1)
    seen[1] = 0
    par = [0] * (N+1)
    child = [[] for _ in range(N+1)]
    seq = []
    while que:
        v = que.popleft()
        seq.append(v)
        for u in adj[v]:
            if seen[u] == -1:
                seen[u] = seen[v] + 1
                par[u] = v
                child[v].append(u)
                que.append(u)
    seq.reverse()

    G = [0] * (N+1)
    child_G = [{} for _ in range(N+1)]
    for v in seq:
        for u in child[v]:
            g = G[u]
            if g in child_G[v]:
                child_G[v][g] += 1
            else:
                child_G[v][g] = 1
        for i in range(N+1):
            if i not in child_G[v]:
                G[v] = i
                break

    #print(G)
    G_ori = G[:]
    GG = G[:]
    seq.reverse()
    for v in seq:
        if v == 1:
            continue
        p = par[v]
        gv = G[v]
        gp = G[p]
        if child_G[p][gv] != 1:
            GG[v] = gp
            if gp in child_G[v]:
                child_G[v][gp] += 1
            else:
                child_G[v][gp] = 1
        else:
            child_G[p][gv] -= 1
            gp_new = mex(child_G[p])
            GG[v] = gp_new
            if gp_new in child_G[v]:
                child_G[v][gp_new] += 1
            else:
                child_G[v][gp_new] = 1
                G[v] = mex(child_G[v])
            child_G[p][gv] += 1

    g = 0
    for a in A:
        g ^= G[a]
    if g == 0:
        print(-1, -1)
    else:
        #print(G)
        #print(g)
        cat = {x: i+1 for i, x in enumerate(A)}
        for v in cat:
            for u in child[v]:
                if G[v] ^ G_ori[u] == g:
                    print(cat[v], u)
                    exit()
            p = par[v]
            if G[v] ^ GG[v] == g:
                print(cat[v], p)
                exit()


if __name__ == '__main__':
    main()