`#include <iostream>
#include <queue>
using namespace std;
const int N=105;
char a[N][N];
int xa,ya,xb,yb;
int dx[4]= {0,1,0,-1},dy[4]= {1,0,-1,0};
int n;
bool st[N][N];
struct Edge
{
    int x,y,w;
    Edge(int x,int y,int w)
    {
        this->x=x;
        this->y=y;
        this->w=w;
    }
};
int bfs()
{
    queue<Edge> q;
    q.push(Edge(xa,ya,0));
    st[xa][xb]=true;
    while(!q.empty())
    {
        Edge t=q.front();
        q.pop();

        for(int i=0; i<4; i++)
        {
            int u=t.x+dx[i],v=t.y+dy[i];
            if(u<=0||u>n||v<=0||v>n)
                continue;
            if(st[u][v])
                continue;
            if(a[t.x][t.y]==a[u][v])
                continue;
            if(a[u][v]=='B') return t.w+1;

            st[u][v]=true;
            q.push(Edge(u,v,t.w+1));
        }
    }
    return -1;
}
int main()
{
    cin>>n;
    for(int i=1; i<=n; i++)
        for(int j=1; j<=n; j++)
        {
            cin>>a[i][j];
            if(a[i][j]=='A')
                xa=i,ya=j;
            if(a[i][j]=='B')
                xb=i,yb=j;
        }
    cout<<bfs();
    //cout << "Hello world!" << endl;
    return 0;
}
`