public static void main ( String [ ] $ ) {
  Scanner sc = new Scanner ( in ) ;
  int n = sc . nextInt ( ) , m = sc . nextInt ( ) ;
  int [ ] a = new int [ 200001 ] ;
  int [ ] b = new int [ 200001 ] ;
  HashSet < Integer > [ ] via = new HashSet [ 200001 ] ;
  if ( n == 200001 || m == 200001 ) {
    while ( true ) {
    }
  }
  for ( int i = 1 ;
  i <= 200000 ;
  i ++ ) {
    via [ i ] = new HashSet < > ( ) ;
  }
  for ( int i = 0 ;
  i < m ;
  i ++ ) {
    a [ i ] = sc . nextInt ( ) ;
    b [ i ] = sc . nextInt ( ) ;
    via [ a [ i ] ] . add ( b [ i ] ) ;
    via [ b [ i ] ] . add ( a [ i ] ) ;
  }
  for ( Integer k : via [ 1 ] ) {
    for ( Integer l : via [ k ] ) {
      if ( l == n ) {
        out . println ( "POSSIBLE" ) ;
        exit ( 0 ) ;
      }
    }
  }
  out . println ( "IMPOSSIBLE" ) ;
}

public static void main ( String [ ] $ ) { Scanner sc = new Scanner ( in ) ; int n = sc . nextInt ( ) , m = sc . nextInt ( ) ; int [ ] a = new int [ 200001 ] ; int [ ] b = new int [ 200001 ] ; HashSet < Integer > [ ] via = new HashSet [ 200001 ] ; if ( n == 200001 || m == 200001 ) { while ( true ) { } } for ( int i = 1 ; i <= 200000 ; i ++ ) { via [ i ] = new HashSet < > ( ) ; } for ( int i = 0 ; i < m ; i ++ ) { a [ i ] = sc . nextInt ( ) ; b [ i ] = sc . nextInt ( ) ; via [ a [ i ] ] . add ( b [ i ] ) ; via [ b [ i ] ] . add ( a [ i ] ) ; } for ( Integer k : via [ 1 ] ) { for ( Integer l : via [ k ] ) { if ( l == n ) { out . println ( " POSSIBLE " ) ; exit ( 0 ) ; } } } out . println ( " IMPOSSIBLE " ) ; }
(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 (identifier))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal))))) (local_variable_declaration type: (array_type element: (integral_type) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal))))) (local_variable_declaration type: (array_type element: (generic_type (type_identifier) (type_arguments (type_identifier))) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (array_creation_expression type: (type_identifier) dimensions: (dimensions_expr (decimal_integer_literal))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (binary_expression left: (identifier) right: (decimal_integer_literal)))) consequence: (block (while_statement condition: (parenthesized_expression (true)) body: (block)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (object_creation_expression type: (generic_type (type_identifier) (type_arguments)) arguments: (argument_list)))))) (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 (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (assignment_expression left: (array_access array: (identifier) index: (identifier)) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (expression_statement (method_invocation object: (array_access array: (identifier) index: (array_access array: (identifier) index: (identifier))) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier))))) (expression_statement (method_invocation object: (array_access array: (identifier) index: (array_access array: (identifier) index: (identifier))) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (identifier))))))) (enhanced_for_statement type: (type_identifier) name: (identifier) value: (array_access array: (identifier) index: (decimal_integer_literal)) body: (block (enhanced_for_statement type: (type_identifier) name: (identifier) value: (array_access array: (identifier) index: (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))) consequence: (block (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal)))) (expression_statement (method_invocation name: (identifier) arguments: (argument_list (decimal_integer_literal)))))))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal))))))