fun main(arr:Array<String>) {
    val susiCount = readLine()!!.toInt()
    susiList.addAll(readLine()!!.split(" ").map { it.toInt() })
    val ans = getAns(0, 0)
    println(ans)
}

val susiList = mutableListOf<Int>()

val dic = mutableMapOf<Int, MutableMap<Int, Int>>()

fun getAns(idx:Int, subTotal:Int):Int {
    if (idx >= susiList.size) {
        return subTotal
    }
    if(!dic.containsKey(idx)) {
        dic[idx] = mutableMapOf()
    }
    dic[idx]!![subTotal]?.let { return it }

    var ans = getAns(idx + 2, subTotal + susiList[idx])
    ans = Math.max(getAns(idx + 1, subTotal), ans)
    dic[idx]!![subTotal] = ans
    return ans
}