#include<iostream>
#include<queue>
using namespace std;

struct node {
	int x,y,rsum;
};
int n,m,sx,sy,fx,fy;
char mp[310][310];
int xx[4] = {-1,1,0,0},yy[4] = {0,0,-1,1};
bool vis[310][310];
queue <node> Q;
node f1;
node f2;
void go_another(int a,int b) {
	for(int i=1 ; i<=n ; i++)
		for(int j=1 ; j<=m ; j++) {
			if(mp[i][j]==mp[a][b]&&i!=a&&j!=b) {
				f2.x = i;
				f2.y = j;
				f2.rsum = f1.rsum+1;
				return ;
			}
		}
}

int main() {
	cin >> n >> m;
	int step = 1;
	for(int i=1 ; i<=n ; i++)
		for(int j=1 ; j<=m ; j++) {
			char c;
			cin >> c;
			if(c=='@')
				sx = i,sy = j;
			else if(c=='=')
				fx = i,fy = j;
			mp[i][j] = c;
		}
	//输入
	/*for(int i=1 ; i<=n ; i++){
		for(int j=1 ; j<=m ; j++)
			cout << mp[i][j] << ' ';
		cout << endl;
	}*/
	vis[1][1] = 1;
	f1.x = sx,f1.y = sy,f1.rsum = 0;
	Q.push(f1);
	while(!Q.empty()) {
		f1 = Q.front();
		int dx,dy;
		for(int i=0 ; i<4 ; i++) {
			//cout<<1<<endl;
			dx = f1.x+xx[i],dy = f1.y+yy[i];
			if(dx>=1&&dx<=n&&dy>=1&&dy<=m&&!vis[dx][dy]&&mp[dx][dy]!='#') {
				if(mp[dx][dy]>='A'&&mp[dx][dy]<='Z') {
					go_another(dx,dy);
					vis[dx][dy] = 1;
					Q.push(f2);
				} else {
					f2.x = dx;
					f2.y = dy;
					f2.rsum = f1.rsum+1;
					vis[dx][dy] = 1;
					Q.push(f2);
					//cout << dx <<" "<< dy <<" "<< f2.rsum << endl;
					if(dx == fx&&dy == fy) {
						cout << f2.rsum;
						return 0;
					}
				}

			}
		}
		Q.pop();
	}
	return 0;
}