浙江大学机试-还是A+B

#include<bits/stdc++.h>
using namespace std;
const int maxn = 105;
int main(){
	int a,b,k;
	int tmp_a,tmp_b;
	int ans;
	bool flag = true;
	while(scanf("%d %d %d",&a,&b,&k)!=EOF){
		if(a==0&&b==0)  break;
		ans = a+b;
		while(k--){
			tmp_a = a%10;
			tmp_b = b%10;
			a = a/10;
			b = b/10;
			if(tmp_a!=tmp_b){
				flag = false;
				break;
			}
			if(a==0||b==0){//提前结束 
				break;
			}
		}
		if(flag == false){
			printf("%d\n",ans);
		}
		else{
			printf("-1\n");
		}
	}
	return 0; 
}