package main

import (
  "bufio"
  "os"
  "strconv"
  "strings"
  "fmt"
)

var reader = bufio.NewReaderSize(os.Stdin, 1000000)
var writer = bufio.NewWriter(os.Stdout)
func NextLine() string {
  buffer := make([]byte, 0)
  for true {
    line, isPrefix, err := reader.ReadLine()
    if err != nil { panic(err) }
    buffer = append(buffer, line...)
    if !isPrefix { break }
  }
  return string(buffer)
}
func NextInt() int {
  n, _ := strconv.Atoi(NextLine())
  return n
}
func NextIntVec() []int {
  L := strings.Split(NextLine(), " ")
  N := make([]int, len(L))
  for i := range N {
    N[i], _ = strconv.Atoi(L[i])
  }
  return N
}
func Write(s interface{}) {
  fmt.Fprintln(writer, s)
}
func WriteIntVec(A []int) {
  S := make([]string, len(A))
  for i, a := range A {
    S[i] = strconv.Itoa(a)
  }
  Write(strings.Join(S, " "))
}
func Output() {
  _ = writer.Flush()
}

func Dijkstra(G [][]int, v int) []int {
  N := len(G)
  D := make([]int, N)
  for i := range D {
    D[i] = -1
  }
  D[v] = 0
  Q := make([]int, N)
  Q[0] = v
  pos := 1
  for _, q := range Q {
    for _, adj := range G[q] {
      if 0 <= D[adj] { continue }
      D[adj] = D[q] + 1
      Q[pos] = adj
      pos++
    }
  }
  return D
}

func Max(A []int) int {
  max := A[0]
  for _, a := range A {
    if max < a { max = a }
  }
  return max
}

func main() {
  Nuv := NextIntVec()
  N, u, v := Nuv[0], Nuv[1] - 1, Nuv[2] - 1
  G := make([][]int, N)
  for i := range G {
    G[i] = make([]int, 0)
  }
  for i := 1; i < N; i++ {
    ab := NextIntVec()
    a, b := ab[0] - 1, ab[1] - 1
    G[a] = append(G[a], b)
    G[b] = append(G[b], a)
  }
  T := Dijkstra(G, u)
  A := Dijkstra(G, v)
  D := make([]int, N)
  for i := range D {
    if A[i] < T[i] { continue }
    if T[i] == A[i] { D[i] = A[i] }
    if T[i] < A[i] { D[i] = A[i] - 1 }
  }
  Write(Max(D))
  Output()
}