Need help with Not So Fast Multiplication

[puma_sof]

hii.. i just joined this site and was trying out the problem not so fast multiplication.. but when i submit it, the grader says that my program exceeded the time limit.. The following is my code.. Can somebody please tell me what to do to improve it's running time??

import java.util.Scanner;
import java.math.BigInteger;

class Main{
public static void main(String args[]){
Scanner in=new Scanner(System.in);
int n=in.nextInt();
BigInteger no[]=new BigInteger[n];
BigInteger multi[]=new BigInteger[n];

	for(int i=0;i<n;i++){
		no[i]=in.nextBigInteger();
		multi[i]=in.nextBigInteger();
	}

	for(int i=0;i<n;i++){
		System.out.println(no[i].multiply(multi[i]));
	}
}

}

[TripleM_sof]

The algorithm for multiplying BigIntegers is too slow for this problem. You have to write your own.