#include<iostream>

#include<queue>

#include<limits.h>

using namespace std;

const int DOWN=1;

const int RIGHT=0;

struct State{

int x,y;

int cost;

int dir;

State(int _x,int _y, int _cost, int _dir):x(_x),y(_y),cost(_cost),dir(_dir){}

State():x(0),y(0),cost(0),dir(RIGHT){};

bool operator < (const State & arg) const

{

return this->cost > arg.cost;

}

};

int main()

{

int n,m;

char graph[110][110];

int vis[110][110][2];

while(cin >>n>>m){

priority_queue<State> q;

//cout << n << " " << m << endl;

for(int i=0;i<n;i++)

{

for(int j=0;j<m;j++){

cin >> graph[i][j];

vis[i][j][0]=INT_MAX;

vis[i][j][1]=INT_MAX;

}

//cout << graph[i] << endl;

}

vis[0][0][1] = 0;

vis[0][0][0] = 0;

State s;

s.x=0;

s.y=0;

s.cost=0;

s.dir=RIGHT;

q.push(s);

while(!q.empty()){

State now = q.top();

int x = now.x;

int y = now.y;

q.pop();

if(x == n - 1 && y == m - 1){

cout << now.cost << endl;

break;

}

State down;

down.dir = DOWN;

if(x + 1 < n){

down.cost = now.cost;

if(now.dir == RIGHT && graph[x][y + 1] == '.' && (y + 1) < m){

down.cost += 1;

}

if(graph[x+1][y] == 'b'){

down.cost += 1;

}

if(down.cost < vis[x + 1][y][DOWN])

{

down.x = x + 1;

down.y = y;

vis[x + 1][y][DOWN] = down.cost;

q.push(down);

}

}

State right;

right.dir = RIGHT;

if(y + 1 < m){

right.cost = now.cost;

if(now.dir == DOWN && graph[x + 1][y] == '.' && (x + 1) < n){

right.cost += 1;

}

if(graph[x][y+1]=='b'){

right.cost += 1;

}

if(right.cost < vis[x][y+1][RIGHT])

{

right.x = x;

right.y = y+1;

vis[x][y+1][RIGHT] = right.cost;

q.push(right);

}

}

}

}

return 0;

}