from sys import stdin,stdout

def main():
    N,M,K = [int(i) for i in input().split()]
    oda = [[] for i in range(N+1)]
    vissza = [[] for i in range(N+1)]
    for i in range(M):
        k,v = [int(i) for i in stdin.readline().split()]
        oda[k].append(v)
        vissza[v].append(k)

    sor = [K]
    volt_vissza = [False]*(N+1)
    volt_vissza[K] = True
    while sor != []:
        P = sor.pop(0)
        for x in vissza[P]:
            if not volt_vissza[x]:
                volt_vissza[x] = True
                sor.append(x)

    sor = [K]
    volt = [False]*(N+1)
    volt[K] = True
    tura = [False]*(N+1)
    for i in oda[K]:
        tura[i] = True
    while sor != []:
        P = sor.pop(0)
        for x in oda[P]:
            if not volt[x]:
                volt[x] = True
                sor.append(x)
                if volt_vissza[x]:
                    for y in oda[x]:
                        tura[y] = True

    tura[K] = False
    t = [i for i in range(1,N+1) if tura[i]]
    print(len(t))
    print(*t)

main()