#include <bits/stdc++.h>
using namespace std;

int n,m,sx,sy,fx,fy,ans;
int d[4][2]={
	{0,-1},
	{0,1},
	{1,0},
	{-1,0},
};
char mp[305][305],sc,tc;
bool vis[305][305];
struct qwp {int x,y,t;};
queue<qwp> q;

void go_to(){
	for(int i=0;i<n;i++){
		for(int j=0;j<m;j++){
			tc=mp[i][j];
			if(tc==sc and i!=fx and j!=fy){
				fx=i;
				fy=j;
				return;		
			}			
		}			
	}
}

int bfs(){
	int x,y,t;
	q.push({sx,sy,0});
	while(!q.empty()){
		x=q.front().x;
		y=q.front().y;
		t=q.front().t;
		q.pop();
		if(mp[x][y]=='=') return t;
		for(int i=0;i<4;i++){
			fx=x+d[i][0];
			fy=y+d[i][1];
			if(fx<0 or fy<0 or fx>=n or fy>=m or mp[fx][fy]=='#' or vis[fx][fy]) 
			   continue;
			vis[fx][fy]=true;
			if(mp[fx][fy]>='A' and mp[fx][fy]<='Z'){
				sc=mp[fx][fy];
				go_to();
			}
			q.push({fx,fy,t+1});
			
		}
	}
	
}

int main(){
	scanf("%d %d",&n,&m);
	for(int i=0;i<n;i++)
		for(int j=0;j<m;j++){
			scanf(" %c",&mp[i][j]);
			if(mp[i][j]=='@') sx=i,sy=j;
		}
			
	ans=bfs();
	printf("%d",ans);		
	return 0;
}

写的有点丑，别介意

评测结果：https://www.luogu.com.cn/record/179125997