import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.NoSuchElementException;

public class Main{
	static FastScanner sc = new FastScanner();
	static PrintWriter out = new PrintWriter(System.out);
	//static String S;
	static int h;
	static int w;
	static char field [][];
	final static int dx []= {0, 1};
	final static int dy []= {1, 0};
	static boolean seen[][];
	static int ans [][];
	//static LinkedList <Integer> adj []; 
	//static boolean visited [][];
	//static TreeMap <Integer, Long> map;
	//static HashMap <Integer, Integer> map;
	//static PriorityQueue <Integer> q;
	
	public static void main(String[] args) {
		h = sc.nextInt();
		w = sc.nextInt();
		field = new char [h][w];
		
		for (int i=0; i<h; i++) {
			field[i] = sc.next().toCharArray();
		}
		
		ans = new int [h][w];
		
		for (int i=0; i<h; i++) {
			Arrays.fill(ans[i], 1_000_000_000);
		}
		
		if (field[0][0]=='#')
			ans[0][0]=1;
		else
			ans[0][0]=0;

		int ny=0;
		int nx=0;
		seen = new boolean [h][w];
		
		for (int y=0; y<h; y++) {
			for (int x=0; x<w; x++) {
				for (int i=0; i<2; i++) {
					ny=y+dy[i];
					nx=x+dx[i];
					if (ny==h || nx==w)
						continue;
					
					if (!seen[ny][nx]) {
						if (field[y][x]=='.' && field[ny][nx]=='#')
							ans[ny][nx] = ans[y][x]+1;
						
						else 
							ans[ny][nx] = ans[y][x];
					}
					
					else {
						if (field[y][x]=='.' && field[ny][nx]=='#')
							ans[ny][nx] = Math.min(ans[y][x]+1, ans[ny][nx]);
						
						else 
							ans[ny][nx] = Math.min(ans[y][x], ans[ny][nx]);
					}
					
					seen[ny][nx]=true;
				}
				
			}
		}
		
		out.println(ans[h-1][w-1]);
		out.flush();
	}
	
	
	
		static class FastScanner {
		    private final InputStream in = System.in;
		    private final byte[] buffer = new byte[1024];
		    private int ptr = 0;
		    private int buflen = 0;

		    private boolean hasNextByte() {
		      if (ptr < buflen) {
		        return true;
		      } else {
		        ptr = 0;
		        try {
		          buflen = in.read(buffer);
		        } catch (IOException e) {
		          e.printStackTrace();
		        }
		        if (buflen <= 0) {
		          return false;
		        }
		      }
		      return true;
		    }

		    private int readByte() {
		      if (hasNextByte()) return buffer[ptr++];
		      else return -1;
		    }

		    private static boolean isPrintableChar(int c) {
		      return 33 <= c && c <= 126;
		    }

		    private void skipUnprintable() {
		      while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
		    }

		    public boolean hasNext() {
		      skipUnprintable();
		      return hasNextByte();
		    }

		    public String next() {
		      if (!hasNext()) throw new NoSuchElementException();
		      StringBuilder sb = new StringBuilder();
		      int b = readByte();
		      while (isPrintableChar(b)) {
		        sb.appendCodePoint(b);
		        b = readByte();
		      }
		      return sb.toString();
		    }

		    public long nextLong() {
		      if (!hasNext()) throw new NoSuchElementException();
		      long n = 0;
		      boolean minus = false;
		      int b = readByte();
		      if (b == '-') {
		        minus = true;
		        b = readByte();
		      }
		      if (b < '0' || '9' < b) {
		        throw new NumberFormatException();
		      }
		      while (true) {
		        if ('0' <= b && b <= '9') {
		          n *= 10;
		          n += b - '0';
		        } else if (b == -1 || !isPrintableChar(b)) {
		          return minus ? -n : n;
		        } else {
		          throw new NumberFormatException();
		        }
		        b = readByte();
		      }
		    }

		    public int nextInt() {
		      return (int) nextLong();
		    }
		    
		    public double nextDouble(){
		    	return Double.parseDouble(next());
		    }

		    public int[] nextIntArray(int N, boolean oneBased) {
		      if (oneBased) {
		        int[] array = new int[N + 1];
		        for (int i = 1; i <= N; i++) {
		          array[i] = sc.nextInt();
		        }
		        return array;
		      } else {
		        int[] array = new int[N];
		        for (int i = 0; i < N; i++) {
		          array[i] = sc.nextInt();
		        }
		        return array;
		      }
		    }

		    public long[] nextLongArray(int N, boolean oneBased) {
		      if (oneBased) {
		        long[] array = new long[N + 1];
		        for (int i = 1; i <= N; i++) {
		          array[i] = sc.nextLong();
		        }
		        return array;
		      } else {
		        long[] array = new long[N];
		        for (int i = 0; i < N; i++) {
		          array[i] = sc.nextLong();
		        }
		        return array;
		      }
		    }
		  }

		}	 





Measured memory_bytes: 23124