/*************************************
* author: marvinthang *
* created: 05.08.2022 11:16:36` *
*************************************/
#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define div ___div
#define left ___left
#define right ___right
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
#define MASK(i) (1LL << (i))
#define FULL(i) (MASK(i) - 1)
#define BIT(x, i) ((x) >> (i) & 1)
#define __builtin_popcount __builtin_popcountll
#define scan_op(...) istream & operator >> (istream &in, __VA_ARGS__ &u)
#define print_op(...) ostream & operator << (ostream &out, const __VA_ARGS__ &u)
#define file(name) if (fopen (name".inp", "r")) { freopen (name".inp", "r", stdin); freopen (name".out", "w", stdout); }
template <class T> scan_op(vector <T>) { for (size_t i = 0; i < u.size(); ++i) in >> u[i]; return in; }
template <class T> print_op(vector <T>) { out << '{'; for (size_t i = 0; i + 1 < u.size(); ++i) out << u[i] << ", "; if (!u.empty()) out << u.back(); return out << '}'; }
template <class U, class V> scan_op(pair <U, V>) { return in >> u.fi >> u.se; }
template <class U, class V> print_op(pair <U, V>) { return out << '(' << u.fi << ", " << u.se << ')'; }
const double PI = 3.1415926535897932384626433832795; // acos(-1.0); atan(-1.0);
const int dir[] = {1, 0, -1, 0, 1, 1, -1, -1, 1}; // {2, 1, -2, -1, -2, 1, 2, -1, 2};
const int MAX = 1002;
int numRow, numCol, numComp, inComp[MAX][MAX];
char grid[MAX][MAX];
bool inside(int x, int y) { return 1 <= x && x <= numRow && 1 <= y && y <= numCol && grid[x][y] != '*'; }
void init(void) {
cin >> numRow >> numCol;
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j)
cin >> grid[i][j];
}
void bfs(int s, int t) {
++numComp;
inComp[s][t] = numComp;
queue <pair <int, int>> q;
q.push(make_pair(s, t));
while (!q.empty()) {
auto [u, v] = q.front(); q.pop();
for (int d = 0; d < 4; ++d) {
int x = u + dir[d];
int y = v + dir[d + 1];
if (inside(x, y) && !inComp[x][y] && grid[x][y] == grid[s][t]) {
inComp[x][y] = numComp;
q.push(make_pair(x, y));
}
}
}
}
vector <int> adj[MAX * MAX];
int dist[MAX * MAX];
void process(void) {
for (int i = 1; i <= numRow; ++i)
for (int j = 1; j <= numCol; ++j)
if (inside(i, j) && !inComp[i][j]) bfs(i, j);
for (int x = 1; x <= numRow; ++x) for (int y = 1; y <= numCol; ++y) if (inside(x, y)) for (int d = 0; d < 4; ++d) {
int u = x + dir[d];
int v = y + dir[d + 1];
if (!inside(u, v) || inComp[x][y] == inComp[u][v]) continue;
adj[inComp[x][y]].push_back(inComp[u][v]);
}
for (int i = 1; i <= numComp; ++i) {
sort(adj[i].begin(), adj[i].end());
adj[i].erase(unique(adj[i].begin(), adj[i].end()), adj[i].end());
}
queue <int> q;
dist[1] = 1;
q.push(1);
while (true) {
int u = q.front(); q.pop();
for (int v: adj[u]) if (!dist[v]) {
dist[v] = dist[u] + 1;
q.push(v);
}
if (q.empty()) return void(cout << dist[u] << '\n');
}
}
int main(void) {
ios_base::sync_with_stdio(false); cin.tie(nullptr); // cout.tie(nullptr);
file("coci1920_r1_zoo");
init();
process();
// cerr << "Time elapsed: " << TIME << " s.\n";
return (0^0);
}
