function Main(input) {
	input = input.trim().split(" ").map((a)=>Number(a));
  var a = input[0];
  var b = input[1];
  var c = input[2];
  if(a == b && a != c){
     console.log(c);
  }else if(a != b && a == c){
    console.log(b);
  }else{
    console.log(a);
  }
}

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