chars = [input() for _ in range(6)]
costs = [0, 1, 1, 1, 1, 2]

inf = 99999

dp = [(0, 0)] * 6

for i in range(16):
    new = [None] * 6
    for j in range(6):
        char = ord(chars[j][i])
        cost = costs[j]
        best = inf
        for prev_char, prev_cost in dp:
            if prev_char <= char:
                best = min(best, prev_cost + cost)
        if char == ord("Q"):
            char = ord("U")
        new[j] = (char, best)
    dp = new
ans = inf
for j in range(6):
    _, cost = dp[j]
    ans = min(ans, cost)
if ans >= inf:
    print("impossible")
else:
    print(ans)