'use strict'

function main(s) {

  s = s.split('\n')[0].split(' ').map(n => Number(n));

  const a = s[0];
  const b = s[1];

  const sum = a + b;

  const ans = (sum < 10) ? sum : 'error';

  console.log(ans);
}

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