#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#define INF 1e9
using namespace std;const int maxn = 20;
int a[maxn][maxn];
int x[maxn],fre[maxn];
int dx[]= {0,0,-1,0,1};
int dy[]= {0,-1,0,1,0};void debug(int n)
{for(int i=0; i<n; i++){for(int j=0; j<n; j++)printf("%d ", a[i][j]);printf("  %d\n", a[i][n]);}puts("**************************************************************");
}void init()
{memset(a,0,sizeof(a));for(int i=0; i<4; i++)for(int j=0; j<4; j++)for(int k=0; k<5; k++){int nx = i+dx[k];int ny = j+dy[k];if(nx>=0 && nx <4 && ny>=0 && ny<4) a[i*4+j][nx*4+ny] = 1;}
}int Guass(int equ,int var)
{
//    debug(16);int row,col,num;num=row=col=0;while(row<equ && col<var){//列非零主int r=row;for(int i=row; i<equ; i++)if(a[i][col]!=0){r=i;break;}if(r!=row){for(int j=col; j<var+1; j++)swap(a[row][j],a[r][j]);}if(a[row][col]==0)//说明有自由变元
        {fre[num++] = col;col++;continue;}//消元for(int i=row+1; i<equ; i++){if(a[i][col]==0) continue;for(int j=col; j<var+1; j++)a[i][j]^=a[row][j];}
//        debug(16);row++;col++;}for(int i=row; i<equ; i++)if(a[i][var]!=0) return INF;int sta=1<<(col-row);//自由变元有col-row个int res=INF;for(int k=0; k<sta; k++) //枚举所有变元
    {int cnt=0;int index=k;for(int j=0; j<num; j++){x[fre[j]]=(index&1);if(x[fre[j]]) cnt++;index>>=1;}for(int i=row-1; i>=0; i--){x[i]=a[i][var];for(col=i+1; col<var; col++)x[i]^=(a[i][col]*x[col]);if(x[i])cnt++;}res=min(cnt,res);}return res;
}int main()
{
//    freopen("in.txt","r",stdin);char s[10][10];for(int i=0; i<4; i++)scanf("%s", s[i]);init();for(int i=0; i<4; i++)for(int j=0; j<4; j++)a[i*4+j][16] = (s[i][j]=='b'? 0:1);int ans1 = Guass(16,16);init();for(int i=0; i<4; i++)for(int j=0; j<4; j++)a[i*4+j][16] = (s[i][j]=='w'? 0:1);int ans2 = Guass(16,16);if(min(ans1,ans2) == INF) puts("Impossible");else printf("%d\n", min(ans1, ans2));return 0;
}