/*
Code by @marlov
*/
#include <iostream>
#include <fstream>
#include <string>
#include <sstream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <iomanip>
#include <utility>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <iterator>
using namespace std;
typedef long long ll;
typedef pair<int,int> pi;
#define maxN 10000000
int dpfront[maxN],dpback[maxN];
int delivery(int N,int K,int L,int position[]){
int ci=0;
while(position[ci]==0){
ci++;
N--;
}
int pos[N];
for(int i=ci;i<N;i++){
pos[i-ci]=position[i];
}
for(int i=0;i<N;i++){
if(i<K) dpfront[i]=min(L,2*pos[i]);
else dpfront[i]=min(L,2*pos[i])+dpfront[i-K];
}
for(int i=0;i<N;i++){
if(i<K) dpback[i]=min(L,2*(L-pos[N-i-1]));
else dpback[i]=min(L,2*(L-pos[N-i-1]))+dpback[N-i-1+K];
}
int result=min(dpback[N],dpfront[N]);
for(int i=1;i<N-1;i++){
result=max(dpfront[i]+dpback[N-i-1],result);
}
return result;
}
/* stuff you should look for
* int overflow, array bounds
* special cases (n=1,n=0?)
* do smth instead of nothing and stay organized
*/
