#include<bits/stdc++.h>
using namespace std;
char auv[305][305];
bool v[305][305];
int n,m,qx,qy;
struct node{
    int x,y,t;
};
queue <node> q;
int fx[4]={1,0,-1,0};
int fy[4]={0,1,0,-1};

void csm(int &x,int &y)
{
    for (int i=1;i<=n;i++){
        for (int j=1;j<=m;j++){
            if (auv[i][j]==auv[x][y]&&(i!=x||j!=y))
            {x=i;y=j;return;}
        } 
    }
}
int main()
{
    cin>>n>>m;
    string s;
    for(int i=1;i<=n;i++){
        cin>>s;
        for(int j=1;j<=m;j++){
            if(s[j-1]=='@'){qx=i;qy=j;}
            auv[i][j]=s[j-1];
        }
    }
    q.push(node{qx,qy,0});
    v[qx][qy]=1;//就是这里,不加这个也对
    while(!q.empty())
    {
        node now=q.front();
        q.pop();
        if(auv[now.x][now.y]=='=')
            {cout<<now.t;return 0;}
        if(auv[now.x][now.y]>='A'&&auv[now.x][now.y]<='Z')
            csm(now.x,now.y);
        for(int i=0;i<=3;i++)
        {
            int ux=now.x+fx[i];
            int uy=now.y+fy[i];
            if(ux>=1&&ux<=n&&uy>=1&&uy<=m&&!v[ux][uy]&&auv[ux][uy]!='#')
            {
                v[ux][uy]=1;
                q.push(node{ux,uy,now.t+1});
            }
        }
    }
    return 0;
}

qwq，有大佬能解释一下嘛？