import java.util.Scanner

object Main {
  def max(a: Int, b: Int): Int = {
    if (a < b) b else a
  }

  def min(a: Int, b: Int): Int = {
    if (a < b) a else b
  }

  def solve(sc: => Scanner): Unit = {
    val s = sc.next
    val (_, _, _, mn, _) = (s + ' ').foldLeft((0, 0, 0, 0, ' '))((acc, c) =>
      (acc, c) match {
        case ((cn, pn, p2n, mn, pc), c) if pc != c =>
          (1, cn, pn, max(mn, min(cn+p2n, pn)), c)
        case ((cn, pn, p2n, mn, pc), c) => (cn + 1, pn, p2n, mn, c)
    })
    println(mn*2)
  }

  def main(args: Array[String]): Unit = {
    val sc: Scanner = new Scanner(System.in)
    solve(sc)
  }
}