N,K=map(int,input().split())
A,M=[],[]
X=[[] for i in range(N)]
G=[[] for i in range(N)]
for i in range(N):
  a,m=map(int,input().split())
  A.append(a)
  M.append(m)
  X[i]=list(map(int,input().split()))
  for j in range(M[i]):
    X[i][j]-=1
    G[X[i][j]].append(i)
INF=10**18
DP=[INF]*N
for i in range(N):
  DP[i]=A[i]
  for j in range(len(X[i])):
    DP[i]=min(DP[i],DP[X[i][j]])
ANS=0
for i in range(N):
  ANS=max(ANS,A[i]-DP[i])
print(ANS)