object Main {
  def main(args: Array[String]): Unit = {
    val s = new Main()
    s.solve()
    s.out.flush()
  }
}

class Main {
  import java.io._
  import java.util.StringTokenizer

  import scala.collection.mutable
  import scala.util.Sorting
  import math.{abs, max, min}
  import mutable.{ArrayBuffer, ListBuffer}
  import scala.reflect.ClassTag

  val MOD = 1000000007
  val out = new PrintWriter(System.out)

  def solve(): Unit = {
    val X, Y = Array.ofDim[Int](3)
    rep(3) { i =>
      X(i) = ni()
      Y(i) = ni()
    }

    val a = Array.ofDim[Double](3)
    def calcAngle(i: Int, j: Int, k: Int) = {
      abs(angle(X(j) - X(i), Y(j) - Y(i), X(k) - X(i), Y(k) - Y(i))) / 2
    }

    def calcR(i: Int, j: Int): Double = {
      import java.awt.geom.Point2D
      val L = Point2D.distance(X(i), Y(i), X(j), Y(j))
      val t1 = Math.tan(a(i))
      val t2 = Math.tan(a(j))
      L / (2 + 1 / t1 + 1 / t2)
    }

    a(0) = calcAngle(0, 1, 2)
    a(1) = calcAngle(1, 2, 0)
    a(2) = calcAngle(2, 0, 1)

//    a map (_ / Math.PI * 180) foreach System.err.println

    val r = Seq(calcR(0, 1), calcR(1, 2), calcR(0, 2))
    out.println(f"${r.max}%.12f")
  }

  /**
    * [-π, π]
    */
  def angle(x1: Int, y1: Int, x2: Int, y2: Int): Double = {
    val sin = -y1 * x2 + x1 * y2  // perp dot product
    val cos = x1 * x2 + y1 * y2   // dot product
    Math.atan2(sin, cos)
  }

  class InputReader(val stream: InputStream) {
    private val reader = new BufferedReader(new InputStreamReader(stream), 32768)
    private var tokenizer: StringTokenizer = _

    def next(): String = {
      while (tokenizer == null || !tokenizer.hasMoreTokens)
        tokenizer = new StringTokenizer(reader.readLine)
      tokenizer.nextToken
    }

    def nextInt(): Int = next().toInt
    def nextLong(): Long = next().toLong
    def nextChar(): Char = next().charAt(0)
  }
  val sc = new InputReader(System.in)
  def ni(): Int = sc.nextInt()
  def nl(): Long = sc.nextLong()
  def nc(): Char = sc.nextChar()
  def ns(): String = sc.next()
  def ns(n: Int): Array[Char] = ns().toCharArray
  def na(n: Int): Array[Int] = map(n)(_ => ni())
  def nal(n: Int): Array[Long] = map(n)(_ => nl())
  def nm(n: Int, m: Int): Array[Array[Char]] = map(n) (_ => ns(m))
  def rep(n: Int, offset: Int = 0)(f: Int => Unit): Unit = {
    var i = offset
    val N = n + offset
    while(i < N) { f(i); i += 1 }
  }
  def rep_r(n: Int, offset: Int = 0)(f: Int => Unit): Unit = {
    var i = n - 1 + offset
    while(i >= offset) { f(i); i -= 1 }
  }

  def map[@specialized A: ClassTag](n: Int)(f: Int => A): Array[A] = {
    val res = Array.ofDim[A](n)
    rep(n)(i => res(i) = f(i))
    res
  }

  def sumL(as: Array[Int]): Long = {
    var s = 0L
    rep(as.length)(i => s += as(i))
    s
  }
}
