code: def sequence(arcs):
      
      succ = {}
      for (i,j) in arcs:
          succ[i] = j
      curr = 1    # first node being visited
      sol = [curr]
      for i in range(len(arcs)-2):
          curr = succ[curr]
          sol.append(curr)
      return sol
docs: sequence: make a list of cities to visit, from set of arcs