fun main() = with(System.`in`.bufferedReader()){
val n = readLine().toInt()
val list = Array(n+1){
ArrayList<Int>()
}
repeat(n){
val (x,y) = readLine().split(" ").map{it.toInt()}
list[y].add(x)
}
list.forEach{
it.sort()
}
var sum = 0
list.forEach{
it.forEachIndexed{ idx, v ->
if(idx==it.lastIndex){
sum += (v-it[idx-1])
}
else if(idx==0){
sum += it[idx+1] - v
}
else{
sum += Math.min(it[idx+1] - v,v-it[idx-1])
}
}
}
println(sum)
}