Language: Java

import java.util.*;
import java.math.*;
         
class Main{
    public static void main(String[] args) {
        
        try(Scanner sc = new Scanner(System.in)){
 
            Long height = sc.nextLong();
            Long width = sc.nextLong();

            BigDecimal ans = new BigDecimal();

            if(height % 2 == 0 || width % 2 == 0){
                ans = height * width / 2;
            }else{
                ans = (height * width + 1) / 2;
            }

            System.out.println(ans);
 
        }catch(Exception e){
            e.printStackTrace();
        }        
    }
}

Compiler output:
Main.java:12: error: no suitable constructor found for BigDecimal(no arguments)
            BigDecimal ans = new BigDecimal();
                             ^
    constructor BigDecimal.BigDecimal(BigInteger,long,int,int) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(char[],int,int) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(char[],int,int,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(char[]) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(char[],MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(String) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(String,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(double) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(double,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(BigInteger) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(BigInteger,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(BigInteger,int) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(BigInteger,int,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(int) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(int,MathContext) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(long) is not applicable
      (actual and formal argument lists differ in length)
    constructor BigDecimal.BigDecimal(long,MathContext) is not applicable
      (actual and formal argument lists differ in length)
Main.java:15: error: incompatible types: long cannot be converted to BigDecimal
                ans = height * width / 2;
                                     ^
Main.java:17: error: incompatible types: long cannot be converted to BigDecimal
                ans = (height * width + 1) / 2;
                                           ^
3 errors