import itertools

def arestes(cami):
    return zip(cami[:-1], cami[1:])

def nTransbords(metro, cami):
    nCanvis=0
    if len(cami)>1:
        vies=arestes(cami)
        i, f = next(vies)
        linia=metro[i][f]['linia']
        for i,f in vies:
            if metro[i][f]['linia']!=linia:
                nCanvis+=1
                linia=metro[i][f]['linia']
    return nCanvis