#include "boxes.h"
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef double ld;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef complex<ld> point;
void debug_out(){cerr << endl;}
template<typename Head, typename... Tail>
void debug_out(Head H, Tail... T){
cerr << H << ' ';
debug_out(T...);
}
#define debug(...) cerr << "(" << #__VA_ARGS__ << "): ", debug_out(__VA_ARGS__)
#define F first
#define S second
#define all(x) x.begin(), x.end()
#define MP(x, y) make_pair(x, y)
const int maxn = 1e7 + 10;
int n, k, l;
ll part[maxn], rpart[maxn];
ll delivery(int N, int K, int L, int p[]) {
n = N;
k = K;
l = L;
for (int i = 0; i < n; i++){
part[i] = min(l, 2 * p[i]);
if (i >= k) part[i] += part[i-k];
}
for (int i = n-1; ~i; i--){
rpart[i] = min(l, 2 * (l - p[i]));
if (i + k < n) rpart[i] += rpart[i+k];
}
ll ans = min(rpart[0], part[n-1]);
for (int i = 0; i < n-1; i++){
ans = min(ans, part[i] + rpart[i+1]);
}
return ans;
}
