#include "boxes.h"
#include <algorithm>
using namespace std;
#define MAX_N 10000000
typedef long long ll;
ll costf[MAX_N+1], coste[MAX_N+1];
ll answer;
long long delivery(int N, int K, int L, int p[]) {
for(int i=0; i<N; i++){
costf[i]=2*(ll)p[i]+(i<K?0:costf[i-K]);
}
for(int i=N-1; i>=0; i--){
coste[i]=(ll)(L-p[i])*2+(i>=N-K?0:coste[i+K]);
}
answer=min(costf[N-1], coste[0]);
if(K>=N){
answer=min(answer, (ll)L);
}
else{
answer = min(answer, costf[N-K-1]+L);
answer = min(answer, coste[K]+L);
}
for(int i=0; i<N-1; i++){
answer=min(answer, costf[i]+coste[i+1]);
if(i+K+1<N){
answer = min(answer, costf[i]+coste[i+K+1]+(ll)L);
}
}
return answer;
}
