def decomp(n):
    D = dict() # dictionnaire vide
    k = 2
    while n > 1:
        exposant = 0
        while n%k == 0:
            exposant = exposant + 1
            n = n/k
        if exposant != 0:
            D[k] = exposant
        k = k+1
        j = 2
        while k%j == 0:
            k = k + 1
    return D