#include "boxes.h"
#include "bits/stdc++.h"
using namespace std;
using ll = long long;
long long delivery(int N, int K, int L, int p[]) {
int pos = 0;
while(p[pos] == 0 && pos < N)
pos++;
if(pos == N)
return 0;
ll ans = 1e18;
ll temp = 0;
int t_pos = pos;
while(t_pos + K - 1 < N && p[t_pos + K - 1] <= L / 2)
{
temp += p[t_pos + K - 1] * 2; // Go and come
t_pos += K;
}
// Either give some souvenirs from other half or stop.
//Begin with left side
int take = 0;
while(t_pos < N && p[t_pos] <= L / 2 && take < K)
{
take++;
t_pos++;
}
//cout << "G" << t_pos << "\n";
if(t_pos != N) {
if(take < K)
{
// Don't go to other half
int r_pos = N - 1;
ll toadd = 0;
if(take > 0)
toadd += p[t_pos - 1] * 2;
while(r_pos - K + 1 >= t_pos)
{
//r_pos -= K;
toadd += (L - p[r_pos - K + 1]) * 2LL;
r_pos -= K;
}
if(t_pos <= r_pos)
toadd += (L - p[t_pos]) * 2LL;
//cout << temp << " " << toadd << " " << t_pos << "\n";
ans = min(ans, temp + toadd);
// Go to other half
toadd = 0;
while(take < K && t_pos < N)
{
t_pos++;
take++;
}
if(take > 0)
toadd += L * 2;
r_pos = N - 1;
while(r_pos - K + 1 >= t_pos)
{
//r_pos -= K;
toadd += (N - p[r_pos - K + 1]) * 2LL;
r_pos -= K;
}
//cout << temp << " " << toadd << " " << t_pos << " " << p[t_pos] << "\n";
if(t_pos < N)
toadd += (L - p[t_pos]) * 2LL;
//cout << temp << " " << toadd << "\n";
ans = min(ans, temp + toadd);
}
} else
{
temp += p[t_pos - 1] * 2LL;
ans = min(ans, temp);
}
//Begin with right side
ll r_pos = N - 1;
temp = 0;
while(r_pos - K + 1 >= pos && p[r_pos - K + 1] >= L / 2)
{
temp += p[r_pos - K + 1] * 2; // Go and come
r_pos -= K;
}
//Begin with right side
take = 0;
while(r_pos >= pos && p[r_pos] >= L / 2 && take < K)
{
take++;
r_pos--;
}
if(r_pos >= pos) {
if(take < K)
{
// Don't go to other half
int l_pos = pos;
ll toadd = 0;
if(take > 0)
toadd += (L - p[r_pos + 1]) * 2;
while(l_pos + K - 1 <= r_pos)
{
//l_pos += K;
toadd += p[l_pos + K - 1] * 2LL;
l_pos += K;
}
if(r_pos >= l_pos)
toadd += p[r_pos] * 2LL;
ans = min(ans, temp + toadd);
// Go to other half
toadd = 0;
l_pos = pos;
while(take < K && r_pos >= pos)
{
r_pos--;
take++;
}
if(take > 0)
toadd += L * 2;
while(l_pos + K - 1 <= r_pos)
{
//l_pos += K;
toadd += p[l_pos + K - 1] * 2LL;
l_pos += K;
}
if(r_pos >= pos)
toadd += p[r_pos] * 2LL;
ans = min(ans, temp + toadd);
}
} else
{
temp += p[r_pos + 1] * 2LL;
ans = min(ans, temp);
}
// ans = min(ans, temp);
return ans;
}
