#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int,int>P;
const double eps = 1e-8;
const int NINF = 0xc0c0c0c0;
const int INF  = 0x3f3f3f3f;
const ll  mod  = 1e9 + 7;
const ll  maxn = 1e6 + 5;
const int N = 200;

int n,m;
char s[N][N];
int f[N][N];

int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin>>n>>m;
	for(int i=1;i<=n;i++) cin>>s[i]+1;
	memset(f,INF,sizeof(f));
    f[1][1]=(s[1][1]=='#');
	for(int i=1;i<=n;i++){
		for(int j=1;j<=m;j++){
			if(i>1) f[i][j]=min(f[i][j],f[i-1][j]+(s[i-1][j]=='.'&&s[i][j]=='#'));
			if(j>1) f[i][j]=min(f[i][j],f[i][j-1]+(s[i][j-1]=='.'&&s[i][j]=='#'));
		}
	}
	cout<<f[n][m]<<'\n';
	return 0;
}