#include <bits/stdc++.h>
using namespace std;
const int N = 1e7 + 7;
vector<long long> v1, v2;
vector<long long> v3, v4;
long long delivery(int n, int k, int l, int *positions){
sort(positions, positions + n);
int idx = 0;
for(; idx < n && positions[idx] <= l / 2; idx++){
v1.push_back(positions[idx]);
}
for(; idx < n; idx++){
v2.push_back(l - positions[idx]);
}
if(!v2.empty()){
reverse(v2.begin(), v2.end());
}
long long ans = 0;
for(int i = k - 1; true; i += k){
ans += (long long)v1[i] * 2ll;
if(i + k >= (int)v1.size()){
for(++i; i < (int)v1.size(); i++){
v3.push_back(v1[i]);
}
break;
}
}
for(int i = k - 1; true; i += k){
ans += (long long)v2[i] * 2ll;
if(i + k >= (int)v2.size()){
for(++i; i < (int)v2.size(); i++){
v4.push_back(v2[i]);
}
break;
}
}
if(v3.empty() || v4.empty()){
if(!v3.empty()){
ans += v3.back() * 2ll;
}
if(!v4.empty()){
ans += v4.back() * 2ll;
}
return ans;
}
return ans;
}
