#include <bits/stdc++.h>
using namespace std;
#define TRACE(x) cerr << #x << " :: " << x << endl
#define _ << " " <<
#define SZ(x) (int)(x).size()
#define ALL(x) (x).begin(),(x).end()
#define FOR(i,a,b) for(int i=(a);i<=(b);++i)
#define RFOR(i,a,b) for (int i=(a);i>=(b);--i)
const int mxN = 1000;
const int mxM = 10;
int N, M;
string G[mxN];
int dp[mxN+1][mxM][1<<mxM];
int main() {
ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
cin >> N >> M;
FOR(i,0,N-1){
cin >> G[i];
}
RFOR(i,N-1,0){
RFOR(j,M-1,0){
FOR(x,0,(1<<M)-1){
if (G[i][j] == '.') {
dp[i][j][x] = dp[i+(j+1)/M][(j+1)%M][x];
} else {
// 1 v 0 h
dp[i][j][x] = min(
dp[i+(j+1)/M][(j+1)%M][x|(1<<j)] + (i==0 || G[i-1][j]=='.' || (x&(1<<j))==0),
dp[i+(j+1)/M][(j+1)%M][x&(~(1<<j))] + (j==0 || G[i][j-1]=='.' || (x&(1<<(j-1)))>0)
);
}
//TRACE(i _ j _ x _ dp[i][j][x]);
}}}
cout << dp[0][0][0] << '\n';
}
