Problem: Consider a grid with H rows and W columns of squares. Let (r, c) denote the square at the r-th row from the top and the c-th column from the left. Each square is painted black or white.

The grid is said to be good if and only if the following condition is satisfied:

* From (1, 1), we can reach (H, W) by moving one square right or down repeatedly, while always being on a white square.



Note that (1, 1) and (H, W) must be white if the grid is good.

Your task is to make the grid good by repeating the operation below. Find the minimum number of operations needed to complete the task. It can be proved that you can always complete the task in a finite number of operations.

* Choose four integers r_0, c_0, r_1, c_1(1 \leq r_0 \leq r_1 \leq H, 1 \leq c_0 \leq c_1 \leq W). For each pair r, c (r_0 \leq r \leq r_1, c_0 \leq c \leq c_1), invert the color of (r, c) - that is, from white to black and vice versa.

Constraints

* 2 \leq H, W \leq 100

Input

Input is given from Standard Input in the following format:


H W
s_{11} s_{12} \cdots s_{1W}
s_{21} s_{22} \cdots s_{2W}
\vdots
s_{H1} s_{H2} \cdots s_{HW}


Here s_{rc} represents the color of (r, c) - `#` stands for black, and `.` stands for white.

Output

Print the minimum number of operations needed.

Examples

Input

3 3
.##
.#.
##.


Output

1


Input

3 3
.##
.#.
.


Output

1


Input

2 2
.
.#


Output

2


Input

4 4
..##
...
.
.


Output

0


Input

5 5
.#.#.
.#.#
.#.#.
.#.#
.#.#.


Output

4

Solution (in JAVA):

Solution:

import java.io.IOException;
import java.io.InputStream;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;

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;
    }

    public boolean hasNext() {
        while (hasNextByte() && !isPrintableChar(buffer[ptr]))
            ptr++;
        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() {
        long nl = nextLong();
        if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE)
            throw new NumberFormatException();
        return (int) nl;
    }

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

public class Main {
    static int MOD = 1000000007;

    static int C(int n, int r) {
        int num = 1;
        for (int i = 1; i <= r; i++) {
            num = num * (n - i + 1) / i;
        }
        return num;
    }

    public static int gcd(int a, int b) {
        return b == 0 ? a : gcd(b, a % b);
    }

    static long lcm(long a, long b) {
        long temp;
        long c = a;
        c *= b;
        while ((temp = a % b) != 0) {
            a = b;
            b = temp;
        }
        return (long) (c / b);
    }

    static long f(long n, Map<Long, Long> map) {
        if (n < 2)
            return 1;
        else if (map.containsKey(n)) {
            return map.get(n);
        } else {
            map.put(n, n * f(n - 2, map));
            return map.get(n);
        }

    }

    public static long factorial(long n) {
        return n <= 0 ? 1 : n * factorial(n - 1);
    }

    private static long calcLCM(long val1, long val2) {
        long maxValue = Math.max(val1, val2);
        long minValue = Math.min(val1, val2);
        long val3 = maxValue * minValue;

        if (minValue == 0)
            return maxValue;

        long temp;
        while ((temp = maxValue % minValue) != 0) {
            maxValue = minValue;
            minValue = temp;
        }

        return (long) (val3 / minValue);
    }

    static String nextPermutation(String s) {
        ArrayList<Character> list = new ArrayList<>();
        for (int i = 0; i < s.length(); i++)
            list.add(s.charAt(i));

        int pivotPos = -1;
        char pivot = 0;
        for (int i = list.size() - 2; i >= 0; i--) {
            if (list.get(i) < list.get(i + 1)) {
                pivotPos = i;
                pivot = list.get(i);
                break;
            }
        }

        if (pivotPos == -1 && pivot == 0)
            return "Final";

        int L = pivotPos + 1, R = list.size() - 1;
        int minPos = -1;
        char min = Character.MAX_VALUE;
        for (int i = R; i >= L; i--) {
            if (pivot < list.get(i)) {
                if (list.get(i) < min) {
                    min = list.get(i);
                    minPos = i;
                }
            }
        }

        Collections.swap(list, pivotPos, minPos);
        Collections.sort(list.subList(L, R + 1));

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < list.size(); i++)
            sb.append(list.get(i));

        return sb.toString();

    }

    public List<String> permutation(List<String> list, String target, String ans) {
        if (target.length() <= 1) {
            list.add(ans + target);
        } else {
            for (int i = 0; i < target.length(); i++) {
                permutation(list, target.substring(0, i) + target.substring(i + 1), ans + target.charAt(i));
            }
        }
        return list;
    }

    public static int lowerbound(int[] a, int key) {
        if (a[a.length - 1] < key)
            return a.length;
        int lb = 0, ub = a.length - 1, mid;
        do {
            mid = (ub + lb) / 2;
            if (a[mid] < key)
                lb = mid + 1;
            else
                ub = mid;
        } while (lb < ub);
        return ub;
    }

    public static int upperbound(int[] a, int key) {
        if (a[a.length - 1] <= key)
            return a.length;
        int lb = 0, ub = a.length - 1, mid;
        do {
            mid = (ub + lb) / 2;
            if (a[mid] <= key)
                lb = mid + 1;
            else
                ub = mid;
        } while (lb < ub);
        return ub;
    }

    public static int count(int[] a, int key) {
        return upperbound(a, key) - lowerbound(a, key);
    }

    public static void quickSort(List<Long> data, int left, int right) {
        if (left >= right)
            return;

        int l = left;
        int r = right;
        long p = data.get((left + right) / 2);
        while (l <= r) {
            while (data.get(l) > p) {
                l++;
            }

            while (data.get(r) < p) {
                r--;
            }
            if (l <= r) {
                long temp = data.get(r);
                data.set(r, data.get(l));
                data.set(l, temp);
                l++;
                r--;
            }
        }

        quickSort(data, left, r);
        quickSort(data, l, right);

        return;

    }

    public static void main(String[] args) {
        FastScanner fs = new FastScanner();
        int h = fs.nextInt();
        int w = fs.nextInt();
        int[] dx = { 1, 0 };
        int[] dy = { 0, 1 };
        char[][] a = new char[h][w];
        for (int i = 0; i < h; i++) {
            a[i] = fs.next().toCharArray();
        }
        int[][] dp = new int[h][w];
        for(int i=0;i<h;i++){
            Arrays.fill(dp[i], Integer.MAX_VALUE);
        }
     
        if (a[0][0] == '#')
            dp[0][0] = 1;
        else
            dp[0][0] = 0;
        
        for (int i = 0; i < h; i++) {
            for (int j = 0; j < w; j++) {
                for (int k = 0; k < 2; k++) {
                    int toX = i + dx[k];
                    int toY = j + dy[k];
                    if ((toX >= h || toY >= w))
                        continue;
                    int add = 0;
                    if (a[toX][toY] == '#' && a[i][j] == '.')
                        add = 1;
                    dp[toX][toY] = Math.min(dp[toX][toY], dp[i][j] + add);
                }
            }
        }
        System.out.println(dp[h - 1][w - 1]);
    }

}