#![allow(non_snake_case)]
#![allow(dead_code)]
#![allow(unused_macros)]
#![allow(unused_imports)]

use std::str::FromStr;
use std::io::*;
use std::collections::*;
use std::cmp::*;

struct Scanner<I: Iterator<Item = char>> {
    iter: std::iter::Peekable<I>,
}

macro_rules! exit {
    () => {{
        exit!(0)
    }};
    ($code:expr) => {{
        if cfg!(local) {
            writeln!(std::io::stderr(), "===== Terminated =====")
                .expect("failed printing to stderr");
        }
        std::process::exit($code);
    }}
}

impl<I: Iterator<Item = char>> Scanner<I> {
    pub fn new(iter: I) -> Scanner<I> {
        Scanner {
            iter: iter.peekable(),
        }
    }

    pub fn safe_get_token(&mut self) -> Option<String> {
        let token = self.iter
            .by_ref()
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect::<String>();
        if token.is_empty() {
            None
        } else {
            Some(token)
        }
    }

    pub fn token(&mut self) -> String {
        self.safe_get_token().unwrap_or_else(|| exit!())
    }

    pub fn get<T: FromStr>(&mut self) -> T {
        self.token().parse::<T>().unwrap_or_else(|_| exit!())
    }

    pub fn vec<T: FromStr>(&mut self, len: usize) -> Vec<T> {
        (0..len).map(|_| self.get()).collect()
    }

    pub fn mat<T: FromStr>(&mut self, row: usize, col: usize) -> Vec<Vec<T>> {
        (0..row).map(|_| self.vec(col)).collect()
    }

    pub fn char(&mut self) -> char {
        self.iter.next().unwrap_or_else(|| exit!())
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.get::<String>().chars().collect()
    }

    pub fn mat_chars(&mut self, row: usize) -> Vec<Vec<char>> {
        (0..row).map(|_| self.chars()).collect()
    }

    pub fn line(&mut self) -> String {
        if self.peek().is_some() {
            self.iter
                .by_ref()
                .take_while(|&c| !(c == '\n' || c == '\r'))
                .collect::<String>()
        } else {
            exit!();
        }
    }

    pub fn peek(&mut self) -> Option<&char> {
        self.iter.peek()
    }
}

const DI: [i64; 4] = [-1, 0, 1, 0];
const DJ: [i64; 4] = [0, -1, 0, 1];

fn main() {
    let cin = stdin();
    let cin = cin.lock();
    let mut sc = Scanner::new(cin.bytes().map(|c| c.unwrap() as char));
    loop {
        let w: usize = sc.get();
        let h: usize = sc.get();
        if w == 0 && h == 0 {
            break;
        }
        let mut ver = vec![Vec::new(); h];
        let mut hor = vec![Vec::new(); h];
        for row in 0..h {
            ver[row] = sc.vec::<usize>(w-1);
            if row != h - 1 {
                hor[row] = sc.vec::<usize>(w);
            }
        }
        let mut q = VecDeque::new();
        q.push_front((0, 0));
        let mut dist = vec![vec![-1; w]; h];
        dist[0][0] = 0;
        while let Some((x, y)) = q.pop_back() {
            let cur = dist[y as usize][x as usize];
            for d in 0..4 {
                let nx = x + DI[d];
                let ny = y + DJ[d];
                if nx < 0 || nx >= w as i64 || ny < 0 || ny >= h as i64 {
                    continue;
                }
                let nx = nx as usize;
                let ny = ny as usize;
                let x = x as usize;
                let y = y as usize;
                if dist[ny][nx] != -1 {
                    continue;
                }
                if nx == x {
                    if ny + 1 == y {
                        if hor[y - 1][x] == 0 {
                            dist[ny][nx] = cur + 1;
                            q.push_front((nx as i64, ny as i64));
                        }
                    } else {
                        if hor[y][x] == 0 {
                            dist[ny][nx] = cur + 1;
                            q.push_front((nx as i64, ny as i64));
                        }
                    }
                } else {
                    if nx + 1 == x {
                        if ver[y][x - 1] == 0 {
                            dist[ny][nx] = cur + 1;
                            q.push_front((nx as i64, ny as i64));
                        }
                    } else {
                        if ver[y][x] == 0 {
                            dist[ny][nx] = cur + 1;
                            q.push_front((nx as i64, ny as i64));
                        }
                    }
                }
            }
        }
        println!("{}", dist[h-1][w-1] + 1);
    }
}



Measured memory_bytes: 5048