const reader = require("readline").createInterface({
  input: process.stdin,
  output: process.stdout
});
let lines = [];
reader.on("line", line => {
  lines.push(line);
});
reader.on("close", () => {
  const check1 = lines.filter(() => {
    return lines[0] === lines[1]
  })
  const check2 = lines.filter(() => {
    return lines[1] === lines[2]
  })
  if (check1 && check2) {
    console.log(lines[0])
  } else if (check1) {
    console.log(lines[0])
  } else {
    console.log(lines[1])
  }

});