#include <bits/stdc++.h>
#include "boxes.h"
using namespace std;

#ifdef DEBUG
auto&operator<<(auto&o,pair<auto,auto>p){return o<<"("<<p.first<<", "<<p.second<<")";}
auto operator<<(auto&o,auto x)->decltype(x.end(),o){o<<"{";int i=0;for(auto e:x)o<<","+!i++<<e;return o<<"}";}
#define debug(X...)cerr<<"["#X"]: ",[](auto...$){((cerr<<$<<"; "),...)<<endl;}(X)
#else
#define debug(...){}
#endif

#define ll long long
#define ld long double
#define endl '\n'
#define st first
#define nd second
#define pb push_back
#define sz(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
#define FOR(i,l,r) for(int i=(l);i<=(r);i++)
#define ROF(i,r,l) for(int i=(r);i>=(l);i--)
int inf=2000000007;
ll infl=1000000000000000007;
ll mod=1000000007;

ll delivery(int n, int k, int l,int p[])
{
	debug(p[0]);
	ll sum=0;
	int L=0,R=n-1;
	while(L+k-1<=R&&2*p[L+k-1]<=l)
	{
		sum+=(ll)2*p[L+k-1];
		L+=k;
	}
	while(R-k+1>=L&&2*p[R-k+1]>l)
	{
		sum+=(ll)2*(l-p[R-k+1]);
		R-=k;
	}
	ll ans=sum;
	if(R-L+1>k) ans+=2*(ll)l;
	else if(R-L+1>0) ans+=(ll)l;
	for(int i=L;i<R;i++)
	{
		ans=min(ans,sum+2*(ll)p[i]+2*(ll)(l-p[i+1]));
	}
	ans=min(ans,sum+2*(ll)p[R]);
	ans=min(ans,sum+2*(ll)(l-p[L]));
	debug(L,R,ans);
    return ans;
}