#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int a[4];
int b[4];
int c[4];
int right(int a,int p){
if(a>>(3-p)&1)return 1;
else return 0;
}
void shangse(int arr[],int x,int y){
arr[x]=arr[x]|(1<<(3-y));
}
void flip(int arr[],int x,int y){
arr[x]=arr[x]^(1<<(3-y));
if(x-1>=0)arr[x-1]^=1<<(3-y);
if(y-1>=0)arr[x]^=1<<(3-y+1);
if(x+1<=3)arr[x+1]^=1<<(3-y);
if(y+1<=3)arr[x]^=1<<(3-y-1);
}
int i,j,b_bushu,c_bushu,minbushu=99999;
char s[20];
int  main(){
//freopen("input2.txt","r",stdin);
for(i=0;i<4;i++){
    scanf("%s",s);
    for(j=0;j<4;j++){
        if(s[j]=='b')shangse(a,i,j);
    }
}
//ceshi
//for(int k=0;k<4;k++){
  //  cout<<a[k]<<endl;
//}
//end
for(i=0;i<16;i++){b_bushu=0;
    for(j=0;j<4;j++)b[j]=a[j];
    ///  sixteen  manipulates
    for(j=0;j<4;j++){
        if(right(i,j))///  the j position is 1 : flip
            {flip(b,0,j);
       b_bushu++;
        }
    }///  the o row is already
    for(int j=0;j<4;j++){
        c[j]=b[j];
   //cout<<"  c[]"<<c[j]<<endl;
    }///   c  is ready
c_bushu=b_bushu;
    for(int m=1;m<4;m++){
        for(int n=0;n<4;n++){
            if(right(b[m-1],n)){flip(b,m,n);b_bushu++;}
            if(!right(c[m-1],n)){flip(c,m,n);c_bushu++;}
        }
    }
    if(b[0]==0&&b[0]==b[1]&&b[1]==b[2]&&b[2]==b[3])///   is the same
       {
       minbushu=min(minbushu,b_bushu);
       }
    if(c[0]==15&&c[0]==c[1]&&c[1]==c[2]&&c[2]==c[3])///   is the same
{

     minbushu=min(minbushu,c_bushu);
}
}
if(minbushu==99999){cout<<"Impossible\n";return 0;}
cout<<minbushu<<endl;
return 0;
}