def solve_graph(input_list):
    vertices_number = input_list[0][0]
    root_id = input_list[0][1]
    edges_number = input_list[0][2]

    vertices = []
    for i in range(0, vertices_number):
        vertices.append([ i, None, None ])

    root_vertice = vertices[root_id]

    edges = []
    for i in range(1, edges_number):
        edges.append(input_list[i])

    def arrange_children(vertice, vertice_parent_id):
        vertice_id = vertice[0]

        def add_child(vertice, child):
            if vertice[1] == None:
                vertice[1] = child
            else:
                vertice[2] = child

        for edge in edges:
            if edge[0] == vertice_id and edge[1] != vertice_parent_id:
                add_child(vertice, vertices[edge[1]])
            elif edge[1] == vertice_id and edge[0] != vertice_parent_id:
                add_child(vertice, vertices[edge[0]])

        if vertice[1] != None:
            arrange_children(vertice[1], vertice_id)
        if vertice[2] != None:
            arrange_children(vertice[2], vertice_id)

    arrange_children(root, -1)
    return root_vertice