class Graph:

    def __init__(self):

        self.V = []

class Vertex:

    def __init__(self, x):

        self.key = x

        self.color = 'white'

        self.d = 10000

        self.f = 10000

        self.pi = None

        self.adj = []

class Solution:

    def Dfs(self, G):

        for u in G.V:

            u.color = 'white'

            u.pi = None

        global time

        time = 0

        for u in G.V:

            if u.color == 'white':

                self.DfsVisit(G, u)

    def DfsVisit(self, G, u):

        global time

        time = time + 1

        u.d = time

        u.color = 'gray'

        for v in u.adj:

            if v.color == 'white':

                v.pi = u

                self.DfsVisit(G, v)

        u.color = 'black'

        time = time + 1

        u.f = time

if __name__ == '__main__':

    u,v,w,x,y,z = [Vertex(i) for i in ['u','v','w','x','y','z']]

    u.adj = [v, x]

    v.adj = [y]

    w.adj = [y, z]

    x.adj = [v]

    y.adj = [x]

    z.adj = [z]

    G = Graph()

    G.V = [u,v,w,x,y,z]

    m = Solution()

    m.Dfs(G)

    for v in G.V:

        print v.key, v.color, v.d, v.f