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