E = int(input())
mo = []
for i in range(E):
    rossz = []
    N = int(input())
    T = list(map(int,input().split()))
    D = {}
    csunya = False
    for _ in range(N-1):
        A,B = map(int,input().split())
        if not csunya:
            if A not in D:
                D[A] = []
            if B not in D:
                D[B] = []
            if T[B-1] == -1:
                D[A].append(B)
            if T[A-1] == -1:
                D[B].append(A)
            if T[A-1] == -1 and len(D[A]) > 0:
                rossz = [A,D[A][0]]
                csunya = True
            elif T[A-1] == 1 and len(D[A]) == 2:
                rossz = [D[A][0],A,D[A][1]]
                csunya = True   
            elif T[B-1] == -1 and len(D[B]) > 0:
                rossz = [B,D[B][0]]
                csunya = True
            elif T[B-1] == 1 and len(D[B]) == 2:
                rossz = [D[B][0],B,D[B][1]]
                csunya = True
    mo.append(rossz)
for eset in mo:
    if len(eset) == 0:
        print("IGEN")
    else:
        print("NEM")
        print(len(eset))
        for k in eset:
            print(k,end=" ")
        print()