AtCoder Beginner Contest 276 B - Adjacency List

N,M=map(int,input().split())
ab=[]
for i in range(M):
    tmp=list(map(int,input().split()))
    ab.append(tmp)

ab.insert(0,[0,0])
data=[[] for i in range(N+1)]

for i in range(1,M+1):
    l=ab[i][0]
    r=ab[i][1]
    data[l].append(r)
    data[r].append(l)


del data[0]

for i,j in enumerate(data):
    kosuu=[len(j)]
    miti=j
    miti.sort()
    kosuu=kosuu+miti
    print(*kosuu)