import scala.collection.mutable
import scala.io.StdIn.*
import scala.math.*
import scala.util.chaining.*

def distance(a: String, b: String): Int =
  val result = Array.fill(2){Array.tabulate(b.length + 1){i => i}}
  for
    i <- a.indices
  do
    val prev = i & 1
    val current = (i & 1) ^ 1
    result(current)(0) = i + 1
    for j <- b.indices do
      if a(i) == b(j) then
        result(current)(j + 1) = min(result(prev)(j), min(result(current)(j), result(prev)(j + 1)) + 1)
      else
        result(current)(j + 1) = min(result(prev)(j), min(result(current)(j), result(prev)(j + 1))) + 1
  result(a.length & 1).last

@main def main =
  val Array(n, m) = readLine().split(' ').map(_.toInt)
  val from = readLine().split(' ').map(_.toInt)
  val to = readLine().split(' ').map(_.toInt)
  val fromStr = mutable.StringBuilder()
  for a <- from do
    fromStr.append(' ')
    for _ <- 0 until a do
      fromStr.append('1')
  val toStr = mutable.StringBuilder()
  for b <- to do
    toStr.append(' ')
    for _ <- 0 until b do
      toStr.append('1')
  val result = distance(fromStr.toString(), toStr.toString())
  println(result)