#![allow(unused, non_snake_case, dead_code, non_upper_case_globals)]
#![macro_use]

use std::cmp::*;
use std::collections::*;
use std::io::*;
use std::mem::*;
use std::num::*;
use std::slice::*;

fn main() {
    let (r, w, e) = (stdin(), stdout(), stderr());
    let mut io = IO::new(r.lock(), w.lock(), e.lock());
    // =============================================== //
    let (h, w): (usize, usize) = (io.read(), io.read());

    let mut s: Vec<Vec<char>> = Vec::new();
    for _ in 0..h {
        let a = io.chars();
        s.push(a);
    }
    let inf = 1 << 30;
    let mut mem = vec![vec![inf; w]; h];

    mem[0][0] = if s[0][0] == '.' { 0 } else { 1 };

    for i in 0..h {
        for j in 0..w {
            // if i == 0 && j == 0 {
            //     continue;
            // }
            // let now = (s[i][j] == '.');
            // let p1 = if i > 0 { mem[i - 1][j] } else { inf };
            // let p2 = if j > 0 { mem[i][j - 1] } else { inf };

            if i + 1 < h {
                if s[i][j] != s[i + 1][j] {
                    mem[i + 1][j] = min(mem[i + 1][j], mem[i][j] + 1);
                } else {
                    mem[i + 1][j] = min(mem[i + 1][j], mem[i][j]);
                }
            }

            if j + 1 < w {
                if s[i][j] != s[i][j + 1] {
                    mem[i][j + 1] = min(mem[i][j + 1], mem[i][j] + 1);
                } else {
                    mem[i][j + 1] = min(mem[i][j + 1], mem[i][j]);
                }
            }
        }
    }
    for j in s.iter() {
        io.debug(j);
    }
    for i in mem.iter() {
        io.debug(i);
    }
    io.writeln((1 + mem[h - 1][w - 1]) / 2);
}

// IO
struct IO<R: Read, W: Write, E: Write> {
    Read: R,
    Write: BufWriter<W>,
    Error: BufWriter<E>,
}
impl<R: Read, W: Write, E: Write> IO<R, W, E> {
    fn new(r: R, w: W, e: E) -> IO<R, W, E> {
        IO {
            Read: r,
            Write: BufWriter::new(w),
            Error: BufWriter::new(e),
        }
    }
    fn read<T>(&mut self) -> T
    where
        T: std::str::FromStr,
    {
        let next: String = self
            .Read
            .by_ref()
            .bytes()
            .map(|c| c.unwrap() as char)
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect();
        next.parse().ok().unwrap()
    }
    fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
    fn readn<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read::<T>()).collect::<Vec<_>>()
    }
    fn readmat<T: std::str::FromStr>(&mut self, n: usize, m: usize) -> Vec<Vec<T>> {
        (0..n).map(|_| self.readn(m)).collect()
    }
    fn write<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
    }
    fn writeln<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
        self.Write.write(b"\n");
    }
    fn debug<S: std::fmt::Debug>(&mut self, val: S) {
        writeln!(self.Error, "(debug ) {:?}", &val);
    }
    fn debug2<S: std::fmt::Debug>(&mut self, val1: S, val2: S) {
        writeln!(self.Error, "(debug2) {:?} -> {:?}", val1, val2);
    }
}


Measured memory_bytes: 4352