static long sumOfLastDig ( long n , long m ) {
  long sum = 0 , k ;
  k = n / m ;
  long [ ] arr = new long [ 10 ] ;
  for ( int i = 0 ;
  i < 10 ;
  i ++ ) {
    arr [ i ] = m * ( i + 1 ) % 10 ;
    sum += arr [ i ] ;
  }
  long rem = k % 10 ;
  long ans = ( k / 10 ) * sum ;
  for ( int i = 0 ;
  i < rem ;
  i ++ ) {
    ans += arr [ i ] ;
  }
  return ans ;
}

static long sumOfLastDig ( long n , long m ) { long sum = 0 , k ; k = n / m ; long [ ] arr = new long [ 10 ] ; for ( int i = 0 ; i < 10 ; i ++ ) { arr [ i ] = m * ( i + 1 ) % 10 ; sum += arr [ i ] ; } long rem = k % 10 ; long ans = ( k / 10 ) * sum ; for ( int i = 0 ; i < rem ; i ++ ) { ans += arr [ i ] ; } return ans ; }
(method_declaration (modifiers) type: (integral_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal)) declarator: (variable_declarator name: (identifier))) (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (identifier) right: (identifier)))) (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))))) (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: (binary_expression left: (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal)))) right: (decimal_integer_literal)))) (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (identifier) right: (decimal_integer_literal)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (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 (expression_statement (assignment_expression left: (identifier) right: (array_access array: (identifier) index: (identifier)))))) (return_statement (identifier))))