>>> from prefix import prefix
>>> llista =['93786545','91876543','93452675','91676543','93787654','97287678','97256543','93876342','97398765','97312345','97345623','97354624','97315463']
>>> prefix(llista, 93)
4
>>> prefix(llista, 973)
5
>>> prefix(llista, 91)
2