// well named variable
const val INF: Int = 100

fun main() {
    // Read input
    val lines = (0 until 6).map{ readln() }

    // DP with index, letter
    val dp = Array<IntArray>(17) { IntArray(26) }
    for (i in 0..25) dp[16][i] = 0
    for (i in 15 downTo 0) {
        for (j in 0..25) {
            dp[i][j] = INF

            for (k in 0..5) {
                val j2: Int = lines[k].get(i).code - 'A'.code
                val j3 = if (lines[k].get(i) == 'Q') 'U'.code - 'A'.code else j2
                val s = if (k == 0) 0 else if (k == 5) 2 else 1
                if (j <= j2) {
                    dp[i][j] = kotlin.math.min(dp[i][j], dp[i + 1][j3] + s)
                }
            }
        }
    }

    if (dp[0][0] == INF) println("impossible")
    else println(dp[0][0])
}