public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  long x = sc . nextLong ( ) ;
  long y = sc . nextLong ( ) ;
  long n = sc . nextLong ( ) ;
  long v [ ] = {
    x , y , y - x , - 1 * x , - 1 * y , x - y };
    n -- ;
    long M = 1000000007 ;
    System . out . print ( ( ( v [ ( int ) n % 6 ] % M ) + M ) % M ) ;
  }
  
public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; long x = sc . nextLong ( ) ; long y = sc . nextLong ( ) ; long n = sc . nextLong ( ) ; long v [ ] = { x , y , y - x , - 1 * x , - 1 * y , x - y } ; n -- ; long M = 1000000007 ; System . out . print ( ( ( v [ ( int ) n % 6 ] % M ) + M ) % M ) ; }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))) (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)))) (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) dimensions: (dimensions) value: (array_initializer (identifier) (identifier) (binary_expression left: (identifier) right: (identifier)) (binary_expression left: (unary_expression operand: (decimal_integer_literal)) right: (identifier)) (binary_expression left: (unary_expression operand: (decimal_integer_literal)) right: (identifier)) (binary_expression left: (identifier) right: (identifier))))) (expression_statement (update_expression (identifier))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (binary_expression left: (parenthesized_expression (binary_expression left: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (cast_expression type: (integral_type) value: (identifier)) right: (decimal_integer_literal))) right: (identifier))) right: (identifier))) right: (identifier)))))))