#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define debug(...) 42
#endif
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
int main() {
ios::sync_with_stdio(false); cin.tie(nullptr);
int n, m; cin >> n >> m;
vector a(n, vector<char>(m));
for (int i = 0; i < n; ++i) {
for (auto &c : a[i]) {
cin >> c;
}
}
vector d(n, vector<int>(m, 1e9));
vector vis(n, vector<bool>(m));
auto inside = [&](int r, int c) {
return 0 <= r && r < n && 0 <= c && c < m && a[r][c] != '.' && !vis[r][c];
};
deque<array<int, 2>> dq{{0, 0}};
d[0][0] = 1;
int res = 0;
while (dq.size()) {
auto [r, c] = dq.front(); dq.pop_front();
if (vis[r][c]) {
continue;
}
res = d[r][c];
vis[r][c] = 1;
for (int k = 0; k < 4; ++k) {
int i = r + dx[k], j = c + dy[k];
if (inside(i, j)) {
if (a[r][c] == a[i][j]) {
d[i][j] = min(d[i][j], d[r][c]);
dq.push_front({i, j});
} else {
d[i][j] = min(d[i][j], d[r][c] + 1);
dq.push_back({i, j});
}
}
}
}
cout << res;
return 0;
}
