function Main(input) {
  input = input.trim()
  input = input.split(" ").map(Number);
if(input[0]===input[2]){

console.log(input[1])
}else if(input[0]==input[1]){

  console.log(input[2])
}else{
  console.log(input[0])
}
}Main(require("fs").readFileSync("/dev/stdin", "utf8"));
