#!/usr/bin/env python3
def s(d,p,i,c):
 return min([50 if c>(x:=d[j][i])else s(d,p,i+1,[x,'U']['Q'==x])+p[j]for j in range(6)])if i<16 else 0
print((list(range(50))+["impossible"])[s([input()for i in range(6)],[0,1,1,1,1,2],0,'A')])