#include <bits/stdc++.h>
#define pii pair<int, int>
using namespace std;
const int MAX = 4004;
char C[MAX][MAX];
int D[MAX][MAX];
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int N, M;
cin >> N >> M;
for (int i = 1; i <= N; ++i) for (int j = 1; j <= M; ++j) cin >> C[i][j];
int ans = 0;
memset(D, 0x3f, sizeof(D));
deque<pii> Q;
D[1][1] = 1;
Q.emplace_back(1, 1);
while (!Q.empty()) {
auto [y, x] = Q.front(); Q.pop_front();
ans = D[y][x];
for (int k = 0; k < 4; ++k) {
int ny = y + "2101"[k] - '1', nx = x + "1012"[k] - '1';
if (ny < 1 || nx < 1 || N < ny || M < nx) continue;
if (C[ny][nx] == '.' || D[ny][nx] < 1e9) continue;
D[ny][nx] = D[y][x] + (C[y][x] != C[ny][nx]);
if (D[y][x] == D[ny][nx]) Q.emplace_front(ny, nx);
else Q.emplace_back(ny, nx);
}
}
cout << ans;
return 0;
}
