public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) , x = sc . nextInt ( ) ;
  int [ ] a = new int [ n ] , b = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int l = sc . nextInt ( ) ;
    int q = sc . nextInt ( ) ;
    if ( l > q ) {
      int t = l ;
      l = q ;
      q = t ;
    }
    a [ i ] = l ;
    b [ i ] = q ;
  }
  int c = 0 ;
  int l = a [ 0 ] ;
  int r = b [ 0 ] ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    if ( l > b [ i ] || r < a [ i ] ) {
      System . out . println ( - 1 ) ;
      System . exit ( 0 ) ;
    }
    l = Math . max ( l , a [ i ] ) ;
    r = Math . min ( r , b [ i ] ) ;
  }
  if ( x < l ) {
    c = l - x ;
  }
  else if ( x > r ) {
    c = x - r ;
  }
  System . out . println ( c ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) , x = sc . nextInt ( ) ; int [ ] a = new int [ n ] , b = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) { int l = sc . nextInt ( ) ; int q = sc . nextInt ( ) ; if ( l > q ) { int t = l ; l = q ; q = t ; } a [ i ] = l ; b [ i ] = q ; } int c = 0 ; int l = a [ 0 ] ; int r = b [ 0 ] ; for ( int i = 1 ; i < n ; i ++ ) { if ( l > b [ i ] || r < a [ i ] ) { System . out . println ( - 1 ) ; System . exit ( 0 ) ; } l = Math . max ( l , a [ i ] ) ; r = Math . min ( r , b [ i ] ) ; } if ( x < l ) { c = l - x ; } else if ( x > r ) { c = x - r ; } System . out . println ( c ) ; }
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type: (integral_type) dimensions: (dimensions_expr (identifier)))) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (identifier))))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (array_access array: (identifier) index: (decimal_integer_literal)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (array_access array: (identifier) index: (decimal_integer_literal)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier))) right: (binary_expression left: (identifier) right: (array_access array: (identifier) index: (identifier))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (unary_expression operand: (decimal_integer_literal))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (decimal_integer_literal)))))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (array_access array: (identifier) index: (identifier)))))) (expression_statement (assignment_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier) (array_access array: (identifier) index: (identifier)))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier))))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier))))))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier))))))