N,M=gets.split.map(&:to_i)
S=gets.chomp
T=gets.chomp
INF=10000
dp = Array.new(N+2).map{Array.new(M+2,INF)}
dp[0][0]=0

(0..N).each{|s|
    (0..M).each{|t|
        if(S[s]==T[t])
            dp[s+1][t+1] = [dp[s+1][t+1], dp[s][t]].min
        else
            dp[s+1][t+1] = [dp[s+1][t+1], dp[s][t]+1].min
        end
        dp[s+1][t] = [dp[s+1][t], dp[s][t]+1].min      
        dp[s][t+1] = [dp[s][t+1], dp[s][t]+1].min      
    }
}
puts dp[N][M]