function Main(input) {
    var input = input.split(' ').map(n => parseInt(n, 10));
    var a = input[0];
    var b = input[1];
    var c = input[2];
    if(a == b) {
        console.log(c);
    } else if(b == c) {
        console.log(a);
    } else {
        console.log(b);
    }
    }
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));