import java.util.*

fun main(args:Array<String>){
    solve()
}

fun solve(){
    val n = readLine()!!.toInt()
    val a = readLine()!!.split(" ").map{it.toLong()}
    val odd = LongArray(n + 2)
    val even = LongArray(n + 2)
    var ans = 0L
    for(i in 0 until n * 2 step 2){
        odd[i / 2 + 1] = a[i]
        even[i / 2 + 1] = a[i + 1]
    }
    for(i in 1 .. n){
        odd[i] += odd[i - 1]
        even[i] += even[i - 1]
    }
    for(i in 0 .. n){
        ans = Math.max(ans, odd[i] + even[n] - even[i] - (even[i] + odd[n] - odd[i]))
    }
    println(ans)
}