function Main(input) {
    const src = input.replace("\n", "").split(" ");
    const a = parseInt(src[0]);
    const b = parseInt(src[1]);
    const c = parseInt(src[2]);
    let ans = a ^ b ^ c;
    console.log(ans);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));
//解説：ビット排他的論理和