1 #include <iostream>
2 #include <string>
3 #include<algorithm>
4 using namespace std;
5 int main(){
6 string str1;
7 string str2;
8 while(cin>>str1>>str2){
9 int size1 = str1.size()-1;
10 int size2 = str2.size()-1;
11 int flag = 0;
12 for(int i=0;i<=size1;i++){
13 if(!(str1[i]>='0' && str1[i] <= '9')){
14 cout<<"error"<<endl;
15 flag = 1;
16 break;
17 }
18 }
19 if(flag) break;
20 for(int i=0;i<=size2;i++){
21 if(!(str2[i]>='0' && str2[i] <= '9')){
22 cout<<"error"<<endl;
23 flag = 1;
24 break;
25 }
26 }
27 if(flag) break;
28 string sum;
29 int carry = 0;
30 int j = 0;
31 while(size1>=0 && size2>=0){
32 int nsum = (str1[size1] - '0') + (str2[size2] - '0') + carry;
33 carry = nsum/10;
34 nsum = nsum%10;
35 sum += to_string(nsum);
36 size1--;
37 size2--;
38 }
39 while(size1 >= 0){
40 int nsum = (str1[size1] - '0') + carry;
41 carry = nsum/10;
42 nsum = nsum%10;
43 sum += to_string(nsum);
44 size1--;
45 }
46 while(size2 >= 0){
47 int nsum = (str2[size2] - '0') + carry;
48 carry = nsum/10;
49 nsum = nsum%10;
50 sum += to_string(nsum);
51 size2--;
52 }
53 if(carry){
54 sum += '1';
55 }
56 reverse(sum.begin(),sum.end());
57 cout<<sum<<endl;
58 }
59 }
