#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
char nxt(char c) {
    if(c=='Q') return 'U';
    return c;
}
/*
5^n with some early breaking
bad!!!!
*/
int main() {
    const int n = 16;
    vector a(n,vector(3,string()));
    for(int i : {0,1,1,1,1,2}) {
        string t; cin >> t;
        for(int j=0;j<n;++j) {
            a[j][i].push_back(t[j]);
        }
    }
    for(auto& r : a) {
        for(auto& i : r) sort(i.begin(),i.end());
    }
    string dp(n*2+1,'Z'+1);
    int ans=1e9;
    auto rec = [&](auto&& self, int at, char c, int mycost) -> void {
        if(mycost>=ans) return;
        if(at==n) {
            ans=mycost;
            return;
        }
        for(int j=0;j<=2;++j) {
            char best = 'Z'+1;
            for(auto& nw : a[at][j]) {
                if(c<=nw) {
                    best=min(best,nxt(nw));
                }
            }
            if(best<='Z') {
                self(self,at+1,best,mycost+j);
            }
        }
    };
    rec(rec,0,'A',0);
    if(ans==1e9) cout << "impossible\n";
    else cout << ans << '\n';
}