if u want u can create a defaultdict which creates an empty list for all the values it get's from group a and append the indeces of those values or u create ur own dictionary append the indeces of the list a and check with list b and print the indeces of each element.

d={}
for i in range(1,n+1):
    w=input()
    if w not in d:
        d[w]=[]
    d[w].append(str(i))

for _ in range(m):
    y=input()
    if y in d:
        print(' '.join(d[y]))
    else:
        print(-1)