public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) ;
  int m = in . nextInt ( ) ;
  Set < Integer > set = new HashSet < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    String str = in . next ( ) ;
    int sIndex = 0 ;
    int gIndex = 0 ;
    for ( int j = 0 ;
    j < m ;
    j ++ ) {
      if ( str . charAt ( j ) == 'G' ) gIndex = j ;
      else if ( str . charAt ( j ) == 'S' ) sIndex = j ;
    }
    if ( sIndex - gIndex > 0 ) set . add ( sIndex - gIndex ) ;
    else {
      System . out . println ( - 1 ) ;
      System . exit ( 0 ) ;
    }
  }
  System . out . println ( set . size ( ) ) ;
  in . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) ; int m = in . nextInt ( ) ; Set < Integer > set = new HashSet < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) { String str = in . next ( ) ; int sIndex = 0 ; int gIndex = 0 ; for ( int j = 0 ; j < m ; j ++ ) { if ( str . charAt ( j ) == ' G ' ) gIndex = j ; else if ( str . charAt ( j ) == ' S ' ) sIndex = j ; } if ( sIndex - gIndex > 0 ) set . add ( sIndex - gIndex ) ; else { System . out . println ( - 1 ) ; System . exit ( 0 ) ; } } System . out . println ( set . size ( ) ) ; in . close ( ) ; }
(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: (generic_type (type_identifier) (type_arguments (type_identifier))) declarator: (variable_declarator name: (identifier) value: (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 (local_variable_declaration type: (type_identifier) 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: (decimal_integer_literal))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (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: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (expression_statement (assignment_expression left: (identifier) right: (identifier))) alternative: (if_statement condition: (parenthesized_expression (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal))) consequence: (expression_statement (assignment_expression left: (identifier) right: (identifier))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (identifier)) right: (decimal_integer_literal))) consequence: (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (binary_expression left: (identifier) right: (identifier))))) alternative: (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 (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list))))) (expression_statement (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))))