/*#pragma GCC optimize("O3")*/
#include<bits/stdc++.h>
//#include <ext/pb_ds/assoc_container.hpp>
//#include <ext/pb_ds/tree_policy.hpp>
//#define ordered_set tree<int, null_type,less<int >, rb_tree_tag,tree_order_statistics_node_update>
#define eps 1e-9
#define MOD1 998244353
#define MOD2 1000000007
#define INV_10 299473306
#define INF 1000000001
#define PI 3.14159265358979323846
using namespace std;
long long delivery(int N, int K, int L, int p[]) {
long long ans=0;
int l=1, r=N;
while(l <= r)
{
long long x=p[min(r, l+K-1)], y=L-p[max(l, r-K+1)], d=L;
if(x <= y)
l=min(r, l+K-1)+1;
else
r=max(l, r-K+1)-1;
ans+=min(min(2*x, 2*y), d);
}
return ans;
}
//size
