#include <bits/stdc++.h>
using namespace std;
const int N = 350;
int dx[4] = {1, 0, -1, 0};
int dy[4] = {0, 1, 0, -1};

struct point { int x, y, t; };
char a[N][N];
bool vis[N][N];
int n, m;

void go(int &x, int &y) // 传送门的函数
{
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= m; j++)
            if ((a[i][j] == a[x][y]) && !((i == x) && (j == y)))
            {
                x = i;
                y = j;
                return;
            }
}
int main()
{
    scanf("%d%d", &n, &m);
    memset(vis, false, sizeof(vis));
    queue<point> Q;
    for (int i = 1; i <= n; i++)
    {
        char s[N]; scanf("%s", s + 1);
        for (int j = 1; j <= m; j++)
        {
            a[i][j] = s[j];
            if (a[i][j] == '@') Q.push(point{i, j, 0}); // 获取起点坐标
        }
    }

    while (!Q.empty())
    {
        point p = Q.front(); Q.pop();
        if (a[p.x][p.y] == '=') { printf("%d\n", p.t); return 0; }
        if (a[p.x][p.y] >= 'A' && a[p.x][p.y] <= 'Z') go(p.x, p.y);

        for (int i = 0; i <= 3; i++)
        {
            int x = p.x + dx[i];
            int y = p.y + dy[i];
            if (x >= 1 && x <= n && y >= 1 && y <= m && a[x][y] != '#' && !vis[x][y])
            {
                vis[x][y] = true;
                Q.push(point{x, y, p.t + 1});
            }
        }
    }
    return 0;
}