main() {
  var number = 123.4;
  print(number.round());
  // 123

  number = 123.5;
  print(number.round());
  // 124

  // 桁数を指定して四捨五入
  const base_number = 10;

  number = 123.44;
  print((number * base_number).round() / base_number);
  // 123.4

  number = 123.45;
  print((number * base_number).round() / base_number);
  // 123.5

  //整数部分を四捨五入
  const base_number_3 = 10;

  number = 144;
  print((number / base_number_3).round() * base_number_3);
  // 140

  number = 145;
  print((number / base_number_3).round() * base_number_3);
  // 150
}