fun main() {
    val (a,b,c) = readLine()!!.split(" ").map{it.toInt()}
    if (a == b && b == c) {
        println(a)
    } else if (a != b && b != c && a != c) {
        println(6 - (a + b + c))
    } else {
        if (a == b) {
            println(c)
        } else if (b == c) {
            println(a)
        } else if (a == c) {
            println(b)
        }
    }
}