public static void main ( String [ ] args ) {
  FastScanner in = new FastScanner ( ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  int t = in . nextInt ( ) ;
  while ( t -- > 0 ) {
    int n = in . nextInt ( ) , xx = in . nextInt ( ) ;
    int d = 0 , h = 0 ;
    int maxDiff = 0 , max = 0 ;
    for ( int i = 0 ;
    i < n ;
    i ++ ) {
      d = in . nextInt ( ) ;
      h = in . nextInt ( ) ;
      maxDiff = Math . max ( maxDiff , d - h ) ;
      max = Math . max ( max , d ) ;
    }
    if ( maxDiff == 0 && max < xx ) out . println ( - 1 ) ;
    else if ( max >= xx ) out . println ( 1 ) ;
    else out . println ( 1 + ( ( xx - max ) + ( maxDiff - 1 ) ) / maxDiff ) ;
  }
  out . flush ( ) ;
}

public static void main ( String [ ] args ) { FastScanner in = new FastScanner ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int t = in . nextInt ( ) ; while ( t -- > 0 ) { int n = in . nextInt ( ) , xx = in . nextInt ( ) ; int d = 0 , h = 0 ; int maxDiff = 0 , max = 0 ; for ( int i = 0 ; i < n ; i ++ ) { d = in . nextInt ( ) ; h = in . nextInt ( ) ; maxDiff = Math . max ( maxDiff , d - h ) ; max = Math . max ( max , d ) ; } if ( maxDiff == 0 && max < xx ) out . println ( - 1 ) ; else if ( max >= xx ) out . println ( 1 ) ; else out . println ( 1 + ( ( xx - max ) + ( maxDiff - 1 ) ) / maxDiff ) ; } out . flush ( ) ; }
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