import java.io._
import java.util.StringTokenizer

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

object Main {
  val MOD = 1000000007
  val out = new PrintWriter(System.out)

  def solve(): Unit = {
    val sc = new InputReader(System.in)
    val N, M = sc.nextInt()
    val cnt = Array.fill[Int](N)(1)
    val flag = Array.ofDim[Boolean](N)
    flag(0) = true
    rep(M) { _ =>
      val x, y = sc.nextInt() - 1
      flag(y) |= flag(x)
      cnt(x) -= 1
      cnt(y) += 1
      if (cnt(x) == 0) flag(x) = false
    }
    val ans = flag.count(identity)
    out.println(ans)
  }


  def main(args: Array[String]): Unit = {
    solve()
    out.flush()
  }


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

    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)
  }
  def rep(n: Int)(f: Int => Unit): Unit = {
    var i = 0
    while(i < n) { f(i); i += 1 }
  }
  def rep_r(n: Int)(f: Int => Unit): Unit = {
    var i = n - 1
    while(i >= 0) { 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
  }

  implicit class ArrayOpts[A](val as: Array[A]) extends AnyVal {
    // todo Orderingだとboxing発生するので自作Orderを用意したい
    def maxByOpt[B: Ordering](f: A => B): Option[A] = {
      if (as.nonEmpty) Some(as.maxBy(f)) else None
    }

    def grpBy[K](f: A => K): mutable.Map[K, ArrayBuffer[A]] = {
      val map = mutable.Map.empty[K, ArrayBuffer[A]]
      rep(as.length)(i => map.getOrElseUpdate(f(as(i)), ArrayBuffer()) += as(i))
      map
    }

    def sumBy[B](f: A => B)(implicit num: Numeric[B]): B = {
      var sum = num.zero
      rep(as.length)(i => sum = num.plus(sum, f(as(i))))
      sum
    }

    def minByEx[B](f: A => B, ixRange: Range = as.indices)(implicit cmp: Ordering[B]): (A, B) = {
      limit(f, ixRange)(cmp.lt)
    }

    def maxByEx[B](f: A => B, ixRange: Range = as.indices)(implicit cmp: Ordering[B]): (A, B) = {
      limit(f, ixRange)(cmp.gt)
    }

    private def limit[B](f: A => B, ixRange: Range)(cmp: (B, B) => Boolean): (A, B) = {
      var limA = as(ixRange.head)
      var limB = f(limA)

      for (i <- ixRange.tail) {
        val a = as(i)
        val b = f(a)
        if (cmp(b, limB)) {
          limA = a
          limB = b
        }
      }
      (limA, limB)
    }
  }

  implicit class IterableOpts[A](val as: Iterable[A]) extends AnyVal {
    def sumBy[B](f: A => B)(implicit num: Numeric[B]): B = {
      as.foldLeft(num.zero)((acc, a) => num.plus(acc, f(a)))
    }
  }

  class UnionFind(n: Int) {
    private val par = Array.ofDim[Int](n)
    par.indices foreach (i => par(i) = i)
    private val rank = Array.ofDim[Int](n)

    def find(x: Int): Int = {
      val stack = ListBuffer[Int]()
      def step(x: Int): Int = {
        if (par(x) == x) x
        else {
          stack += x
          step(par(x))
        }
      }

      val res = step(x)
      stack foreach (i => par(i) = res)
      res
    }

    def unite(x: Int, y: Int): Unit = {
      val x1 = find(x)
      val y1 = find(y)
      if (x1 != y1) {
        if (rank(x1) < rank(y)) {
          par(x1) = y1
        } else {
          par(y1) = x1
          if (rank(x1) == rank(y1)) rank(x1) += 1
        }
      }
    }
  }
}


Measured memory_bytes: 42792