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

public class Main {
	public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        BigInteger a = in.nextBigInteger();
        BigInteger b = in.nextBigInteger();
        System.out.println(a.add(b).longValueExact());
	}
}

如题，置顶回答已经谈及这个问题了