fun main() {
    val builder = StringBuilder()

    val bArr = readInputLine().split(" ").map { it.toInt() }

    for (i in 1..10) {
        if (!bArr.contains(i)) {
            builder.appendln(i)
            break
        }
    }

    print(builder.toString())
}

fun readInputLine(): String {
    return readLine()!!
}