cost = 100

        # for going downwards
        if (a[1] < b[1] and a[0] in [0, 80, 160] and a[1] < 160):
            cost = 0
        # for going upwards
        elif (a[1] > b[1] and a[0] in [40, 120] and a[1] >= 40):
            cost = 0
        # for going right
        elif(a[0] < b[0]) :
            if (a[1] == 160 and a[0]//40 in [0, 2, 4]):
                cost = 0
            elif (a[1] == 39 and a[0]//40 in [1, 3]):
                cost = 0