import java.util.*

fun main(args: Array<String>) {
    val n = readLine()!!.toInt()
    val a = readLine()!!.split(' ').map { it.toInt() }
    var hom = 0L
    var tem = 0L
    for (i in 0 until n) {
        hom += a[2 * i + 1]
        tem += a[2 * i]
    }
    var max = hom - tem
    for (i in 0 until n) {
        hom += a[2 * i] - a[2 * i + 1]
        tem += a[2 * i + 1] - a[2 * i]
        max = Math.max(max, hom - tem)
    }
    println(max)
}