function Main(input){
    input = input.split("\n");
    tmp = input[0].split(" ");

    var a = parseInt(tmp[0],10);
    var b = parseInt(tmp[1],10);
    var c = parseInt(tmp[2],10);
    if (a == b){
        console.log("%d",c);
    } else if(a == c){
        console.log("%d",b);
    } else{
        console.log("%d",a);
    }
}

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