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

struct cs {
	int cx, cy;
};

struct node {
	int x, y, s;
};

int N, M; 
char mp[305][305];
bool vis[305][305];
int minL = INT_MAX;

cs css[2][26];
int dX[4] = {-1, 0, 0, 1};
int dY[4] = {0, -1, 1, 0};

void bfs(int sx, int sy) {
	queue<node> q;
	node n = {sx, sy, 0};
	q.push(n);
	while(!q.empty()) {
		node tmp = q.front();
		q.pop();
		int tx = tmp.x;
		int ty = tmp.y;
		int ts = tmp.s;
		//找到对应存储的传送点坐标，并修改当前的tx, ty 
		if(mp[tx][ty] >= 'A' && mp[tx][ty] <= 'Z') {
			int ttx = tx;
			int tty = ty;
			if(tx == css[0][mp[ttx][ty] - 'A'].cx) {
				tx = css[1][mp[ttx][tty] - 'A'].cx;
				ty = css[1][mp[ttx][tty] - 'A'].cy;
			}
			else if(tx == css[1][mp[ttx][tty] - 'A'].cx) {
				tx = css[0][mp[ttx][tty] - 'A'].cx; 
				ty = css[0][mp[ttx][tty] - 'A'].cy;
			}
		}
		//朝四个方向移动 
		for(int i = 0; i < 4; i++) {
			int nx = tx + dX[i];
			int ny = ty + dY[i];
			if(nx >= 1 && nx <= N && ny >= 1 && ny <= M && mp[nx][ny] != '#' && !vis[nx][ny]) {
				if(mp[nx][ny] == '=') {
					printf("%d", ts + 1);
					return ;
				}
				else if(mp[nx][ny] == '.') {
					vis[nx][ny] = 1;
					tmp = {nx, ny, ts + 1};
				} else {
					tmp = {nx, ny, ts + 1};
				}
				q.push(tmp);
			}
		}
	}	
}

int main() {
	int sx, sy;
	scanf("%d%d", &N, &M);
	getchar();
	for(int i = 1; i <= N; i++) {
		for(int j = 1; j <= M; j++) {
			mp[i][j] = getchar();
			if(mp[i][j] == '@') {
				sx = i;
				sy = j;
			} else if(mp[i][j] <= 'Z' && mp[i][j] >= 'A') {//二维数组的第0行和第1行相互为一组传送点 
				if(css[0][mp[i][j] - 'A'].cx == 0) {
					css[0][mp[i][j] - 'A'].cx = i;
					css[0][mp[i][j] - 'A'].cy = j;
				} else {
					css[1][mp[i][j] - 'A'].cx = i;
					css[1][mp[i][j] - 'A'].cy = j;
				}
			}
		}
		getchar();
	}
	vis[sx][sy] = 1;
	bfs(sx, sy);
	return 0;
} 

试了很多次，2，3，4，6出不了答案诶