#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main() {
int n, m;
cin >> n >> m;
string s;
vector<vector<int>> closed(n, vector<int>(m, false));
for (int i = 0; i < n; i++) {
cin >> s;
for (int j = 0; j < m; j++) {
if (s[j] == '#')
closed[i][j] = true;
}
}
vector<vector<vector<int>>> mem(n, vector<vector<int>>(m, vector<int>(1LL << m, -1)));
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
for (int k = 0; k < (1LL << m); k++) {
if (i == 0 && j == 0) {
mem[i][j][k] = closed[i][j];
continue;
}
if (!closed[i][j]) {
mem[i][j][k] = min(mem[i - (j == 0)][(j + m - 1) % m][k], mem[i - (j == 0)][(j + m - 1) % m][k ^ (1LL << j)]);
continue;
}
if (j != 0 && !((k && (1LL << j)) || (k && (1LL << (j - 1))))) {
mem[i][j][k] = min(mem[i][j - 1][k], mem[i][j - 1][k ^ (1LL << j)]);
if (!closed[i][j - 1]) {
mem[i][j][k]++;
}
continue;
}
if (j == 0 || !(k && (1LL << j)) && (k && (1LL << (j - 1)))) {
mem[i][j][k] = min(mem[i - (j == 0)][(j + m - 1) % m][k], mem[i - (j == 0)][(j + m - 1) % m][k ^ (1LL << j)]) + 1;
continue;
}
if (k && (1LL << j)) {
if (i != 0 && closed[i - 1][j]) {
mem[i][j][k] = min(mem[i - (j == 0)][(j + m - 1) % m][k], mem[i - (j == 0)][(j + m - 1) % m][k ^ (1LL << j)] + 1);
}
else {
mem[i][j][k] = min(mem[i - (j == 0)][(j + m - 1) % m][k], mem[i - (j == 0)][(j + m - 1) % m][k ^ (1LL << j)]) + 1;
}
continue;
}
}
}
}
int ans = INT_MAX;
for (int i : mem[n - 1][m - 1])
ans = min(ans, i);
cout << ans << '\n';
}
