#include <iostream>
#include <vector>
using namespace std;
struct Queue {
	struct node {
		int x, y;
		int step;
	};
	node u[1010100];
	int head = 1, tail = 0;
	inline void reuse() {
		head = 1, tail = 0;
	}
	inline void push(node a) {
		u[++tail] = a;
	}
	inline void pop_front() {
		++head;
	}
	inline void pop_back() {
		--tail;
	}
	inline node front() {
		return u[head];
	}
	inline node back() {
		return u[tail];
	}
	inline int size() {
		return tail - head + 1;
	}
	inline bool empty() {
		return tail < head;
	}
} q;
int dis[1010][1010];
char a[1010][1010];
int dir[4][2] = {
	{0, 1},
	{1, 0},
	{0, -1},
	{-1, 0}
};
char Getchar() {
	char c = getchar();
	while (c != '@' && c != '.' && c != '=' && c != '#' && !(c >= 'A' && c <= 'Z')) c = getchar();
	return c;
}
vector<pair<int, int> > g[30];
int main() {
	int n, m, x, y;
	scanf("%d%d", &n, &m);
	for (int i = 1; i <= n; ++i) {
		for (int j = 1; j <= m; ++j) {
			a[i][j] = Getchar();
			if (a[i][j] >= 'A' && a[i][j] <= 'Z') {
				g[a[i][j] - 'A'].emplace_back(i, j);
			}
			if (a[i][j] == '@') {
				x = i, y = j;
			}
		}
	}
//	for (int i = 1; i <= n; ++i) for (int j = 1; j <= m; ++j) {
//			cout << a[i][j];
//			if (j == m) cout << '\n';
//		}
//	cout << g['W' - 'A'].size() << '\n';
	q.push({x, y, 0});
	dis[x][y] = -1;
	while (!q.empty()) {
		Queue::node frt = q.front();
		q.pop_front();
		if (a[frt.x][frt.y] == '=') {
			return printf("%d\n", frt.step), 0;
		}
		for (int i = 0; i < 4; ++i) {
			int _x = frt.x + dir[i][0], _y = frt.y + dir[i][1];
			if (_x < 1 || _y < 1 || _x > n || _y > m || a[_x][_y] == '#') continue;
			if (a[_x][_y] >= 'A' && a[_x][_y] <= 'Z') {
				pair<int, int> qwq;
				if (g[a[_x][_y] - 'A'][0] != make_pair(_x, _y)) {
					qwq = g[a[_x][_y] - 'A'][0];
				} else {
					qwq = g[a[_x][_y] - 'A'][1];
				}
				if (dis[qwq.first][qwq.second] == 0 || dis[qwq.first][qwq.second] > frt.step + 1) {
					q.push({qwq.first, qwq.second, frt.step + 1});
					dis[qwq.first][qwq.second] = frt.step + 1;
				}
			}
			if ((dis[_x][_y] > frt.step + 1 || dis[_x][_y] == 0)) {
				dis[_x][_y] = frt.step + 1;
				q.push({_x, _y, dis[_x][_y]});
			}

		}
	}
	return 0;
}