type table=array[1..4,1..4]of byte;
var sz,back:table;
    turn:array[-1..1,-1..1]of byte;
    out:shortint;
procedure init;
var i,j:shortint;
    c:char;
begin
     out:=-1;
     fillchar(sz,sizeof(sz),0);
     fillchar(back,sizeof(back),0);
     fillchar(turn,sizeof(turn),0);
     for i:=1 to 4 do
         begin
              for j:=1 to 4 do
                  begin
                       read(c);
                       while not (c in['B','W']) do
                             read(c);
                       if c='B' then
                          sz[i,j]:=1
                                else
                          sz[i,j]:=0
                  end;
              readln;
         end;
     back:=sz;
     for i:=-1 to 1 do
         begin
              for j:=-1 to 1 do
                  begin
                       read(c);
                       while not (c in['1','0']) do
                             read(c);
                       if c='1' then
                          turn[i,j]:=1
                                else
                          turn[i,j]:=0;
                  end;
              readln;
         end;
end;
procedure mark(a,b:byte);
var i,j:shortint;
begin
     for i:=-1 to 1 do
         for j:=-1 to 1 do
             if ((a+i) in[1..4])and((b+j) in [1..4]) then
                if turn[i,j]=1 then
                   sz[a+i,b+j]:=(sz[a+i,b+j]+1)mod 2;
end;
procedure make;
var s:table;
    t:word;
    i,j,k,l:byte;
    q:boolean;
begin
     for t:=0 to 65535 do
         begin
              fillchar(s,sizeof(s),0);
              i:=t;
              for k:=0 to 15 do
                  begin
                       l:=i mod 2;
                       i:=i div 2;
                       s[k div 4+1,k mod 4+1]:=l;
                  end;
              for i:=1 to 4 do
                  for j:=1 to 4 do
                      if s[i,j]=1 then
                         mark(i,j);
              q:=true;
              k:=sz[1,1];
              for i:=1 to 4 do
                  begin
                  for j:=1 to 4 do
                      if sz[i,j]<>k then
                         begin
                              q:=false;
                              break;
                         end;
                  if not q then
                     break;
                  end;
              if q then
                 begin
                      k:=0;
                      for i:=1 to 4 do
                          for j:=1 to 4 do
                              if s[i,j]<>0 then
                                 inc(k);
                      if (k<out)or(out=-1) then
                         out:=k;
                 end;
              sz:=back;
         end;
end;
procedure print;
begin
     if out=-1 then
        writeln('Impossible')
               else
        writeln(out);
end;
begin
     init;
     make;
     print;
end.