#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <cstring>
using namespace std;
int main() {
       int a, b;
cin>>a>>b;
if(a+b>=10)
cout<<"error"<<endl;
else
cout<<a+b<<endl;
	system("pause");
	return 0;
}