用大数存储就OK

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


public class Main {
	public static void main(String[] args) {
		Scanner sc=new Scanner(System.in);
		BigInteger sum=BigInteger.ZERO;
		
		while(true) {
			BigInteger a=sc.nextBigInteger();
			if(a.equals(new BigInteger("0"))) {
				break;
			}
			sum=sum.add(a);
		}
		System.out.println(sum);
	}
}