#define fast ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0)
#include <bits/stdc++.h>
using namespace std;
#define sqr 200
#define mid (l+r)/2
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define lb lower_bound
#define ub upper_bound
#define ins insert
#define era erase
#define C continue
#define mem(dp,i) memset(dp,i,sizeof(dp))
#define mset multiset
typedef long long ll;
typedef short int si;
typedef long double ld;
typedef pair<int,int> pi;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<pi> vpi;
typedef vector<pll> vpll;
const ll mod=1e9+7;
const ll inf= 4e18;
const ld pai=acos(-1);
#include "boxes.h"
ll P[1009];
ll solve ( ll N , ll K ,ll L ) {
ll ans = 0 , last = 0;
ll k = K ;
for(int i =0 ;i < N ;i ++ ) {
ll x1 = abs ( last - P[i] );
ll x2 = L - abs ( last - P[i] );
ans += min ( x1 , x2 );
last = P[i];
k -- ;
if ( x2 <= x1 ) k = K ;
if ( k == 0){
ans += min ( abs(last-0) , L - abs(last-0) ) ;
last = 0 ;
k = K ;
}
}
if ( k ) ans += min ( abs(last-0) , L - abs(last-0) ) ;
return ans ;
}
long long delivery(int N, int K, int L, int p[]) {
for ( int i = 0 ; i < N ; i ++ )P[i] = p[i];
return solve ( N , K , L ) ;
}
