fn main() {
      let amount = 100;
      let percent = 2.5;
      let res = f64::floor((amount as f64) * (percent/100.0)) as i64;
      println!("amount: {}, percent: {} result: {}", amount, percent, res);
      let amount = 100;
      let percent = -2.5;
      let res = f64::floor((amount as f64) * (percent/100.0)) as i64;
      println!("amount: {}, percent: {} result: {}", amount, percent, res);
}