Computing Combinations with Java

cnk.java

import java.math.*;

public class cnk{
	public static BigInteger cnk(int n, int k)
	{
		BigInteger fenzi = new BigInteger("1");
		BigInteger fenmu = new BigInteger("1");
		for(int i=n-k+1; i <= n; i++){
			String s = Integer.toString(i);
			BigInteger stobig = new BigInteger(s);
			fenzi = fenzi.multiply(stobig);
		}
		for(int j=1; j <= k; j++){
			String ss = Integer.toString(j);
			BigInteger stobig2 = new BigInteger(ss);
			fenmu = fenmu.multiply(stobig2);
		}
		BigInteger result = fenzi.divide(fenmu);
		return result;
	}
	public static void main(String args[])
	{
		int n = 100, k = 2;
		BigInteger result = cnk(n, k);
		System.out.println(result.toString());
	}
}

if i give n=32145 and k=12345 ( ie 5 digit input) it is not working