n, m = gets.chomp.split(" ").map(&:to_i)
s = gets.chomp
t = gets.chomp

INF = 10 ** 9
dp = []
(s.length + 1).times do |i|
  dp[i] = []
  (t.length + 1).times do |j|
    dp[i][j] = INF
  end
end

dp[0][0] = 0
(s.length + 1).times do |i|
  (t.length + 1).times do |j|
    # 変更
    if i > 0 && j > 0
      if s[i - 1] == t[j - 1]
        dp[i][j] = [dp[i][j], dp[i-1][j-1]].min
      else
        dp[i][j] = [dp[i][j], dp[i-1][j-1] + 1].min
      end
    end
    # 削除
    if i > 0
      dp[i][j] = [dp[i][j], dp[i-1][j] + 1].min
    end
    # 挿入
    if j > 0
      dp[i][j] = [dp[i][j], dp[i][j-1] + 1].min
    end
  end
end

puts dp[-1][-1]