#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {
cerr<<vars<<" = ";
string delim="";
(...,(cerr<<delim<<values,delim=", "));
cerr<<"\n";
}
#else
#define deb(...) logger(#__VA_ARGS__, __VA_ARGS__)
template<typename ...Args>
void logger(string vars, Args&&... values) {}
#endif
#define pb push_back
#define sz(x) (int)(x.size())
typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
template<typename T> inline void maxa(T& a,T b){a=max(a,b);}
template<typename T> inline void mina(T& a,T b){a=min(a,b);}
ll delivery(int N, int K, int L, int positions[]){
ll ans=0;
vector<int> pos;
for(int i=0;i<N;i++){
if(positions[i])
pos.pb(positions[i]);
}
int n=sz(pos);
vector<ll> pref(n),suff(n);
for(int i=0;i<n;i++){
if(i<K){
pref[i]=min(2*pos[i],L);
} else{
pref[i]=min(2*pos[i],L)+pref[i-K];
}
}
for(int i=n-1;i>=0;i--){
if(n-i-1<K){
suff[i]=min(2*(L-pos[i]),L);
} else{
suff[i]=min(2*(L-pos[i]),L)+suff[i+K];
}
}
ans=min(pref[n-1],suff[0]);
for(int i=0;i<n-1;i++){
mina(ans,pref[i]+suff[i+1]);
}
return ans;
}
