#!/usr/bin/env python3

lines = tuple(input() for _ in range(6))

prefix = '@' # '@' < 'A'
turns = 0
for i in range(16):
    vals = [(0, lines[0][i])] + [(2, lines[5][i])] + [(1, lines[j][i]) for j in [1,2,3,4]]
    filtered_vals = list(t[::-1] for t in vals if t[1] >= prefix[-1])
    if not filtered_vals:
        print('impossible')
        break
    c, t = min(filtered_vals)
    prefix += c
    turns += t
else:
    print(turns)