fun main(arr:Array<String>) {
    val susiCount = readLine()!!.toInt()
    susiList.addAll(readLine()!!.split(" ").map { it.toInt() })
    susiList.indices.forEach { getAns(it) }
    println(getAns(susiList.lastIndex))
}

val susiList = mutableListOf<Int>()

val dic = mutableMapOf<Int, Int>()

fun getAns(idx:Int):Int {
    if(idx == 0) {
        return susiList[0]
    }
    if(idx == 1) {
        return susiList.take(2).max()!!
    }

    dic[idx]?.let { return it }
    var ans = getAns(idx - 1)
    ans = Math.max(getAns(idx-2) + susiList[idx], ans)
    dic[idx] = ans
    return ans
}