use std::cmp::min;

fn main() {
    let mut nm: String = String::new();
    std::io::stdin().read_line(&mut nm).ok();
    let nm: Vec<usize> = nm.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let mut s: String = String::new();
    std::io::stdin().read_line(&mut s).ok();
    let s: Vec<char> = s.trim().chars().collect();
    let mut t: String = String::new();
    std::io::stdin().read_line(&mut t).ok();
    let t: Vec<char> = t.trim().chars().collect();

    let n: usize = nm[0];
    let m: usize = nm[1];

    const LIMIT: usize = 2000;
    let mut dp: Vec<Vec<usize>> = vec![vec![LIMIT; m+1]; n+1];
    dp[0][0] = 0;
    for i in -1..(n as isize) {
        let s_char = if i >= 0 { s[i as usize] } else { 'X' };
        for j in -1..(m as isize) {
            let t_char = if j >= 0 { t[j as usize] } else { 'X' };
            if i == -1 && j == -1 {
                continue;
            }
            /*
            del: sから現在見ている1文字を削除 = sのindexを1すすめる
            ins: tで現在見ている1文字と同じ文字をsに追加する = tのindexを1すすめる
            upd: tで現在見ている1文字とsを同じ文字にする = s, tのindexを1すすめる
            */
            if i >= 0 && j >= 0 {
                let ui = i as usize;
                let uj = j as usize;
                if s_char == t_char {
                    dp[ui + 1][uj + 1] = min(dp[ui][uj], dp[ui+1][uj+1]);
                } else {
                    dp[ui + 1][uj + 1] = min(dp[ui][uj] + 1, dp[ui+1][uj+1]);
                }
            }
            if i >= 0 {
                let ui = i as usize;
                let uj1 = (j+1) as usize;
                dp[ui+1][uj1] = min(dp[ui+1][uj1], dp[ui][uj1]+1);
            }
            if j >= 0 {
                let ui1 = (i+1) as usize;
                let uj = j as usize;
                dp[ui1][uj+1] = min(dp[ui1][uj+1], dp[ui1][uj] + 1);
            }
        }
    }
    println!("{}", dp[n][m]);
}