class Yukicoder
  def initialize
    n, m = gets.chomp.split.map(&:to_i)
    s = gets.chomp
    t = gets.chomp
    dp = Array.new(n+2){ Array.new(m+2, [n,m].max)}

    dp[0][0] = 0

    0.upto(n) do |i|
      0.upto(m) do |j|
        if s[i] == t[j]
          dp[i+1][j+1] = [dp[i+1][j+1], dp[i][j]].min
        else
          dp[i+1][j+1] = [dp[i+1][j+1], dp[i][j]+1].min
        end
        dp[i+1][j] = [dp[i+1][j], dp[i][j]+1].min
        dp[i][j+1] = [dp[i][j+1], dp[i][j]+1].min
      end
    end

    p dp[n][m]
  end
end

Yukicoder.new