"""
Created on: Sat Nov 14 05:23:16 2020
Author: vila@cs.upc.edu
"""
def check_noms(llnoms):
    
    ldef = []
    n = 1
    for l in llnoms:
        nom, k = check_lnoms(l)
        if nom != '':
            ldef.append([n, nom, k])
        n += 1
    return ldef

def check_lnoms(l):
    k = l[0]
    if len(l[1]) < k:
        return l[1], 1
    else:
        ref = l[1][:k]
        for pos in range(2, len(l)):
            nom = l[pos]
            if nom[:k] != ref:
                return nom, pos
        return '', -1