#include<iostream>
#include<cstdio>
#include<map>
#include<cstring>
using namespace std;
int head,tail=1,step[10000];
int e_[4][2]={{0,1},{1,0},{-1,0},{0,-1}},now[10][10],ans;
struct node{
    int map[10][10];
    int f;
};node e[10000];
map<string,bool>hash;
bool pd(node z){
    string s="";
    for(int i=1;i<=4;i++){
        for(int j=1;j<=4;j++){
            s+=z.map[i][j]+‘1‘;
        }
    }
    if(hash[s]==1)return true;
    else {hash[s]=1;return false;}
}
bool judge(int x,int y){
    if(x<=4&&x>=1&&y<=4&&y>=1&&e[head].map[x][y]!=0&&e[head].map[x][y]!=e[head].f)
    return true;
    return false;
}
void copy(){
    for(int i=1;i<=4;i++)
        for(int j=1;j<=4;j++)
            e[tail].map[i][j]=e[head].map[i][j];
}
bool equ(int a1,int a2,int a3,int a4){if(a1!=a2||a2!=a3||a3!=a4||a4!=a1)return 0;return 1;}
bool check(int w)
{
    for(int i=1;i<=4;i++)
    {
        if(equ(e[w].map[i][1],e[w].map[i][2],e[w].map[i][3],e[w].map[i][4]))return 1;
        if(equ(e[w].map[1][i],e[w].map[2][i],e[w].map[3][i],e[w].map[4][i]))return 1;
    }
    if(equ(e[w].map[1][1],e[w].map[2][2],e[w].map[3][3],e[w].map[4][4]))return 1;
    if(equ(e[w].map[1][4],e[w].map[2][3],e[w].map[3][2],e[w].map[4][1]))return 1;
    return 0;
}
void bfs(){
    while(head<tail){
        head++;
        for(int i=1;i<=4;i++){
            for(int j=1;j<=4;j++){
                if(e[head].map[i][j]==0){
                    for(int k=0;k<4;k++){
                        int xx=e_[k][0]+i,yy=e_[k][1]+j;
                        if(judge(xx,yy)){
                            tail++;
                            copy();
                            e[tail].map[xx][yy]=0;
                            if(e[head].f==1){
                                e[tail].map[i][j]=-1;
                                e[tail].f=-1;
                            }
                            else{
                                e[tail].map[i][j]=1;
                                e[tail].f=1;
                            }step[tail]=step[head]+1;
                            if(check(tail)){ans=min(ans,step[tail]);return;}
                            if(pd(e[tail]))tail--;
                        }
                    }
                }
            }
        }
    }
}
char ch[10];
int main(){
    
    ans=0x7fffffff;
    for(int i=1;i<=4;i++){
        cin>>ch;
        for(int j=1;j<=4;j++){
            if(ch[j-1]==‘W‘)now[i][j]=1;
            if(ch[j-1]==‘B‘)now[i][j]=-1;
            if(ch[j-1]==‘O‘)now[i][j]=0;
        }
    }
    for(int i=1;i<=4;i++)
        for(int j=1;j<=4;j++)
            e[1].map[i][j]=now[i][j];
    e[1].f=1;
    bfs();
    head=0;tail=1;
    memset(e,0,sizeof(e));
    memset(step,0,sizeof(step));
    hash.clear();
    for(int i=1;i<=4;i++)
        for(int j=1;j<=4;j++)
            e[1].map[i][j]=now[i][j];
    e[1].f=-1;
    bfs();
    cout<<ans;
}