#include <bits/stdc++.h>
using namespace std;
#define int long long
const int MAXN = 1e7+4;
int P[MAXN];
int lpr[MAXN];
int rpr[MAXN];
int N, K, L;
int ans(int a, int b){
int M = 0;
for (int i=a; i<b; i++) M = max(M, P[i+1]-P[i]);
return min(min(P[b] + min(L-P[b], P[b]), L-P[a] + min(L-P[a], P[a])), 2*L - 2*M);
}
int delivery(signed n, signed k, signed l, signed p[]){
N=n;K=k;L=l;for (int i=0; i<n; i++) P[i] = p[i];
int r = n%k;
for (int i=0; i<n; i++){
if (i%k == k-1) lpr[i] += ans(i-k+1, i);
if (i>0) lpr[i] += lpr[i-1];
}
for (int i=n-1; i>=0; i--){
if (i%k == n%k) rpr[i] += ans(i, i+k-1);
if (i<n-1) rpr[i] += rpr[i+1];
}
int res = 1e18;
for (int i=0; i<n; i+=k){
res = min(res, (i?lpr[i-1]:0) + (r?ans(i, i+r-1):0) + rpr[i]);
}
return res;
}
