public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  N = scan . nextInt ( ) ;
  a = scan . nextInt ( ) - 1 ;
  b = scan . nextInt ( ) - 1 ;
  int M = scan . nextInt ( ) ;
  int [ ] [ ] A = new int [ N ] [ N ] ;
  int [ ] [ ] B = new int [ N ] [ N ] ;
  for ( int i = 0 ;
  i < M ;
  i ++ ) {
    int x = scan . nextInt ( ) - 1 ;
    int y = scan . nextInt ( ) - 1 ;
    A [ x ] [ y ] = 1 ;
    A [ y ] [ x ] = 1 ;
    B [ x ] [ y ] = 1 ;
    B [ y ] [ x ] = 1 ;
  }
  scan . close ( ) ;
  int [ ] [ ] C = new int [ N ] [ N ] ;
  for ( int l = 0 ;
  l < N ;
  l ++ ) {
    if ( B [ a ] [ b ] != 0 ) {
      System . out . println ( B [ a ] [ b ] ) ;
      System . exit ( 0 ) ;
    }
    for ( int i = 0 ;
    i < N ;
    i ++ ) {
      for ( int j = 0 ;
      j < N ;
      j ++ ) {
        int t = 0 ;
        for ( int k = 0 ;
        k < N ;
        k ++ ) {
          t += B [ i ] [ k ] * A [ k ] [ j ] ;
        }
        t = t % q ;
        C [ i ] [ j ] = t ;
      }
    }
    for ( int i = 0 ;
    i < N ;
    i ++ ) {
      for ( int j = 0 ;
      j < N ;
      j ++ ) {
        B [ i ] [ j ] = C [ i ] [ j ] ;
      }
    }
  }
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; N = scan . nextInt ( ) ; a = scan . nextInt ( ) - 1 ; b = scan . nextInt ( ) - 1 ; int M = scan . nextInt ( ) ; int [ ] [ ] A = new int [ N ] [ N ] ; int [ ] [ ] B = new int [ N ] [ N ] ; for ( int i = 0 ; i < M ; i ++ ) { int x = scan . nextInt ( ) - 1 ; int y = scan . nextInt ( ) - 1 ; A [ x ] [ y ] = 1 ; A [ y ] [ x ] = 1 ; B [ x ] [ y ] = 1 ; B [ y ] [ x ] = 1 ; } scan . close ( ) ; int [ ] [ ] C = new int [ N ] [ N ] ; for ( int l = 0 ; l < N ; l ++ ) { if ( B [ a ] [ b ] != 0 ) { System . out . println ( B [ a ] [ b ] ) ; System . exit ( 0 ) ; } for ( int i = 0 ; i < N ; i ++ ) { for ( int j = 0 ; j < N ; j ++ ) { int t = 0 ; for ( int k = 0 ; k < N ; k ++ ) { t += B [ i ] [ k ] * A [ k ] [ j ] ; } t = t % q ; C [ i ] [ j ] = t ; } } for ( int i = 0 ; i < N ; i ++ ) { for ( int j = 0 ; j < N ; j ++ ) { B [ i ] [ j ] = C [ i ] [ j ] ; } } } }
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