public static void main ( String [ ] args ) {
  FastScanner input = new FastScanner ( ) ;
  int n = input . nextInt ( ) ;
  int count = 0 ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    TreeSet < Integer > set = new TreeSet < > ( ) ;
    int j = 1 ;
    int sum = i ;
    while ( j < n ) {
      sum = sum % n ;
      set . add ( sum ) ;
      sum *= i ;
      j ++ ;
    }
    if ( set . size ( ) == n - 1 ) count ++ ;
  }
  System . out . println ( count ) ;
}

public static void main ( String [ ] args ) { FastScanner input = new FastScanner ( ) ; int n = input . nextInt ( ) ; int count = 0 ; for ( int i = 1 ; i < n ; i ++ ) { TreeSet < Integer > set = new TreeSet < > ( ) ; int j = 1 ; int sum = i ; while ( j < n ) { sum = sum % n ; set . add ( sum ) ; sum *= i ; j ++ ; } if ( set . size ( ) == n - 1 ) count ++ ; } System . out . println ( count ) ; }
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