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inputt = input().split()
dni, spotkania = inputt
dni = int(dni)
spotkania = int(spotkania)
lista_spotkan = [[] for _ in range(dni)]
lista_spotkan[0] = [0 for _ in range(spotkania+1)]
lista_spotkan[0][0] = spotkania
for i in range(1,dni):
    inputt = input().split()
    for liczba in inputt:
        lista_spotkan[i].append(int(liczba))
maxi = 0
lista = [1 for _ in range(len(lista_spotkan[-1]))]
for i in range(dni-1, 0, -1):
    lista[0] = 0
    maxi = max(sum(lista), maxi)
    nastepna = [0 for _ in range(len(lista_spotkan[i-1]))]
    for j in range(1,len(lista)):
        nastepna[lista_spotkan[i][j]]+=lista[j]
    for k in range(len(nastepna)):
        if nastepna[k]==0:
            nastepna[k]+=1
    lista = nastepna
lista[0] = 0
maxi = max(sum(lista), maxi)
print(maxi)