function Main(input) {
	const arr = input.split(' ');
	const a = parseInt(arr[0], 10);
	const b = parseInt(arr[1], 10);

	if(a + b < 10) {
		console.log(a + b);
	} else {
		console.log("error");
	};

Main(require("fs").readFileSync("/dev/stdin", "utf8"));