fun main() {
val n = readLine().toInt()
val array = readLine()
.split(' ')
.map { it.toInt() }
val m = (n / 2) - 1
var result = 0
for (i in 0..m) {
result += kotlin.math.abs(array[i] - array[n - 1 - i])
}
println(result)
}