process.stdin.resume();
process.stdin.setEncoding('utf8');
// Here your code !
process.stdin.on('data', function (chunk) {
    var lines = chunk.toString().split(' ');
    var A = parseInt(lines[0]);
    var B = parseInt(lines[1]);
    
    if(A+B >=10){
        console.log("error");
    }else{
        console.log(A+B);
    }
});