Karatsuba Algorithm without BigInteger usage

I have been trying to implement Karatsuba Algorithm in java without using BigInteger. My code is applicable only when both the integers are same & have same number of digits. I do not get the correct answer however I get answer which is quite near to the right one. For instance I get 149 when 12*12. I can not figure out what is wrong with my code since I believe I have done everything right (by the book). Here's my code. ``` public static void main(String[] args) { long ans=karatsuba(12,12); System.out.println(ans); } private static long karatsuba(long i, long j) { if (i<10 || j<10){ return i*j; } int n=getCount(i); long a=(long) (i/Math.pow(10, n/2)); long b=(long) (i%Math.pow(10, n/2)); long c=(long) (j/Math.pow(10, n/2)); long d=(long) (j%Math.pow(10, n/2)); long first=karatsuba(a,c); long second=karatsuba(b,d); long third=karatsuba(a+b,c+d); return ((long) ((first*Math.pow(10, n))+((third-first-second)*Math.pow(10,n/2))+third)); } private static int getCount(long i) { String totalN=Long.toString(i); return totalN.length(); } ``` EDIT: Thanks to Ziyao Wei, the problem was replacing "third" by "second". However I have another issue now which is: If karatsuba(1234,5678) is called I get the correct answer however when I call karatsuba(5678,1234) I do not get the right answer. Could anyone possibly know the reason for that? My updated code is: ``` public static void main(String[] args) { //wrong answer long ans=karatsuba(5678,1234); System.out.println(ans); //correct answer long ans1=karatsuba(1234,5678); System.out.println(ans1); } private static long karatsuba(long i, long j) { if (i<10 || j<10){ return i*j; } int n=getCount(i); long a=(long) (i/Math.pow(10, n/2)); long b=(long) (i%Math.pow(10, n/2)); long c=(long) (j/Math.pow(10, n/2)); long d=(long) (j%Math.pow(10, n/2)); long first=karatsuba(a,c); long second=karatsuba(b,d); long third=karatsuba(a+b,c+d); return ((long) ((first*Math.pow(10, n))+((third-first-second)*Math.pow(10, n/2))+second)); } ``` UPDATE: I have managed to round up value for "n/2" hence it solves the problem however if numbers more than four digits are used bugs occur. Here is my updated code: ``` public static void main(String[] args) { System.out.println(Math.round(5.00/2)); //correct answer long ans=karatsuba(5678,1234); System.out.println(ans); //correct answer long ans1=karatsuba(1234,5678); System.out.println(ans1); //wrong answer long ans2=karatsuba(102456,102465); System.out.println(ans2); } private static long karatsuba(long i, long j) { if (i<10 || j<10){ return i*j; } double n=Math.round(getCount(i)); long a=(long) (i/Math.pow(10, Math.round(n/2))); long b=(long) (i%Math.pow(10, Math.round(n/2))); long c=(long) (j/Math.pow(10, Math.round(n/2))); long d=(long) (j%Math.pow(10, Math.round(n/2))); long first=karatsuba(a,c); long second=karatsuba(b,d); long third=karatsuba(a+b,c+d); return ((long) ((first*Math.pow(10, Math.round(n)))+((third-second-first)*Math.pow(10, Math.round(n/2)))+second)); } private static double getCount(long i) { String totalN=Long.toString(i); return totalN.length(); } ``` If somebody comes up with the solution for larger numbers (more than four digits) without using BigInteger then please do let me know. Thanks.