#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
char chess[4][4];
int global=0;    //全局
vector<int>ANS;

void readdata()
{
    for(int i=0;i<4;i++)for(int j=0;j<4;j++)cin>>chess[i][j];
}
void change(int i, int j)
{
    if(chess[i][j]=='b'){chess[i][j]='w';return;}
    if(chess[i][j]=='w'){chess[i][j]='b';return;}
}
void alter(int i,int j)
{
    change(i,j);
    if(i>0)change(i-1,j);
    if(i<3)change(i+1,j);
    if(j>0)change(i,j-1);
    if(j<3)change(i,j+1);
}
bool ok()
{
    char color=chess[0][0];
    for(int i=0;i<4;i++)for(int j=0;j<4;j++)if(chess[i][j]!=color)return false;
    return true;
}
void search(int m,int n)
{
    if(ok()){ANS.push_back(global);return;}
    if(m>=4)return;
        alter(m,n);
        global++;
        if(n<3)search(m,n+1);else search(m+1,0);
        alter(m,n);
        global--;
        if(n<3)search(m,n+1);else search(m+1,0);

}
void show()
{
    if(!ANS.empty())cout<<*min_element(ANS.begin(),ANS.end());
    else cout<<"Impossible";
}
int main()
{
    ANS.reserve(100);
    readdata();
    search(0,0);
    show();
}