public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int N = sc . nextInt ( ) ;
  int [ ] boll = new int [ N ] ;
  boolean [ ] red = new boolean [ N ] ;
  for ( int n = 0 ;
  n < N ;
  n ++ ) {
    boll [ n ] = 1 ;
    red [ n ] = ( n == 0 ) ;
  }
  int M = sc . nextInt ( ) ;
  for ( int m = 0 ;
  m < M ;
  m ++ ) {
    int x = sc . nextInt ( ) - 1 ;
    int y = sc . nextInt ( ) - 1 ;
    if ( red [ x ] ) red [ y ] = true ;
    boll [ y ] ++ ;
    if ( boll [ x ] <= 1 ) red [ x ] = false ;
    boll [ x ] -- ;
  }
  System . out . println ( count ( red ) ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int N = sc . nextInt ( ) ; int [ ] boll = new int [ N ] ; boolean [ ] red = new boolean [ N ] ; for ( int n = 0 ; n < N ; n ++ ) { boll [ n ] = 1 ; red [ n ] = ( n == 0 ) ; } int M = sc . nextInt ( ) ; for ( int m = 0 ; m < M ; m ++ ) { int x = sc . nextInt ( ) - 1 ; int y = sc . nextInt ( ) - 1 ; if ( red [ x ] ) red [ y ] = true ; boll [ y ] ++ ; if ( boll [ x ] <= 1 ) red [ x ] = false ; boll [ x ] -- ; } System . out . println ( count ( red ) ) ; }
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