def corregeix_nota(ln,index):
    if len(ln) == 0:
        return -1
    elif index == 0 or index > len(ln[0]) - 1:
        return -1
    else:
        modificats = 0
        for subll in ln:
            if 4.75 < subll[index] < 5:
                subll[index] = 5.0
                modificats += 1
        return modificats