public static void main ( String [ ] args ) {
  Scanner s = new Scanner ( System . in ) ;
  int n = s . nextInt ( ) ;
  int min = Integer . MAX_VALUE ;
  int max = Integer . MIN_VALUE ;
  int [ ] firsts = new int [ n ] ;
  int [ ] seconds = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int first = s . nextInt ( ) ;
    int second = s . nextInt ( ) ;
    if ( first < min ) {
      min = first ;
    }
    if ( second > max ) {
      max = second ;
    }
    firsts [ i ] = first ;
    seconds [ i ] = second ;
  }
  boolean found = false ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( firsts [ i ] == min && seconds [ i ] == max ) {
      System . out . println ( i + 1 ) ;
      found = true ;
      break ;
    }
  }
  if ( ! found ) {
    System . out . println ( - 1 ) ;
  }
}

public static void main ( String [ ] args ) { Scanner s = new Scanner ( System . in ) ; int n = s . nextInt ( ) ; int min = Integer . MAX_VALUE ; int max = Integer . MIN_VALUE ; int [ ] firsts = new int [ n ] ; int [ ] seconds = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { int first = s . nextInt ( ) ; int second = s . nextInt ( ) ; if ( first < min ) { min = first ; } if ( second > max ) { max = second ; } firsts [ i ] = first ; seconds [ i ] = second ; } boolean found = false ; for ( int i = 0 ; i < n ; i ++ ) { if ( firsts [ i ] == min && seconds [ i ] == max ) { System . out . println ( i + 1 ) ; found = true ; break ; } } if ( ! found ) { System . out . println ( - 1 ) ; } }
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