fun main(args: Array<String>) {

    val list = readLine()!!.split(" ").map { it.toInt() }


    for (i in 0 until 10) {
        if (i == 9) {
            println(10)
            break
        }
        if (list[i] != i + 1) {
            println(i + 1)
            break
        }
    }
}