package microsoft;

import java.util.Scanner;

public class Q3 {

private static final int MM = 1000000000;

private static boolean B(char[][] map, int x, int y){

if(x < map.length && y<map[0].length && map[x][y] == '.')

return false;

else

return true;

}

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

int N = sc.nextInt();

int M = sc.nextInt();

sc.nextLine();

if(N == 0 || M == 0){

System.out.println(0);

return;

}

char[][] map = new char[N][M];

for(int i=0; i<N; i++){

map[i] = sc.nextLine().toCharArray();

}

int[][] hengzhe = new int[N][M];

int[][] shuzhe = new int[N][M];

hengzhe[0][0] = (B(map,0,0) ? 1 : 0);

shuzhe[0][0] = MM;

for(int j=1; j<M; j++){

hengzhe[0][j] = hengzhe[0][j-1] + (B(map,0,j) ? 1 : 0);

shuzhe[0][j] = MM;

}

if(1<N) shuzhe[1][0] = (B(map,0,1) ? 0 : 1);

hengzhe[1][0] = MM;

for(int i=2; i<N; i++){

shuzhe[i][0] = shuzhe[i-1][0] + (B(map,i,0) ? 1 : 0);

hengzhe[i][0] = MM;

}

for(int i=1; i<N; i++){

for(int j=1; j<M; j++){

shuzhe[i][j] = Math.min(shuzhe[i-1][j],hengzhe[i-1][j] + (B(map,i-1,j+1) ? 0 : 1) )

+ (B(map,i,j) ? 1 : 0);

hengzhe[i][j] = Math.min(hengzhe[i][j-1],shuzhe[i][j-1] + (B(map,i+1,j-1) ? 0 : 1) )

+ (B(map,i,j) ? 1 : 0);

}

}

System.out.println(Math.min(hengzhe[N-1][M-1], shuzhe[N-1][M-1]));

}

}