#include <iostream>
#include <iomanip>
#include <sstream>
#include <vector>
#include <string>
#include <set>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <stack>
#include <queue>
#include <deque>
#include <algorithm>
#include <functional>
#include <iterator>
#include <limits>
#include <numeric>
#include <utility>
#include <type_traits>
#include <cmath>
#include <cassert>
#include <cstdio>
using namespace std;
using namespace placeholders;
using LL = long long;
using ULL = unsigned long long;
using VI = vector< int >;
using VVI = vector< vector< int > >;
using VS = vector< string >;
using SS = stringstream;
using PII = pair< int, int >;
using VPII = vector< pair< int, int > >;
template < typename T = int > using VT = vector< T >;
template < typename T = int > using VVT = vector< vector< T > >;
template < typename T = int > using LIM = numeric_limits< T >;
template < typename T > inline istream& operator>>( istream &s, vector< T > &v ){ for ( T &t : v ) { s >> t; } return s; }
template < typename T > inline ostream& operator<<( ostream &s, const vector< T > &v ){ for ( int i = 0; i < int( v.size() ); ++i ){ s << ( " " + !i ) << v[i]; } return s; }
template < typename T > inline T fromString( const string &s ) { T res; istringstream iss( s ); iss >> res; return res; }
template < typename T > inline string toString( const T &a ) { ostringstream oss; oss << a; return oss.str(); }
#define NUMBERED( name, number ) NUMBERED2( name, number )
#define NUMBERED2( name, number ) name ## _ ## number
#define REP1( n ) REP2( NUMBERED( REP_COUNTER, __LINE__ ), n )
#define REP2( i, n ) REP3( i, 0, n )
#define REP3( i, m, n ) for ( int i = ( int )( m ); i < ( int )( n ); ++i )
#define GET_REP( a, b, c, F, ... ) F
#define REP( ... ) GET_REP( __VA_ARGS__, REP3, REP2, REP1 )( __VA_ARGS__ )
#define FOR( e, c ) for ( auto &&e : c )
#define ALL( c ) begin( c ), end( c )
#define AALL( a ) ( std::remove_all_extents< decltype( a ) >::type * )a, ( std::remove_all_extents< decltype( a ) >::type * )a + sizeof( a ) / sizeof( std::remove_all_extents< decltype( a ) >::type )
#define DRANGE( c, p ) ( c ).begin(), ( c ).begin() + ( p ), ( c ).end()
#define SZ( v ) ( (int)( v ).size() )
#define EXIST( c, e ) ( ( c ).find( e ) != ( c ).end() )
template < typename T > inline bool chmin( T &a, const T &b ){ if ( b < a ) { a = b; return true; } return false; }
template < typename T > inline bool chmax( T &a, const T &b ){ if ( a < b ) { a = b; return true; } return false; }
#define PB push_back
#define EM emplace
#define EB emplace_back
#define BI back_inserter
#define MP make_pair
#define fst first
#define snd second
#define DUMP( x ) cerr << #x << " = " << ( x ) << endl
// セグメント木のユーティリティ
inline int chl( const int k )
{
return k * 2 + 1;
}
inline int chr( const int k )
{
return k * 2 + 2;
}
inline int mid( const int l, const int r )
{
return ( l + r ) / 2;
}
#define LEFT( k, l, r ) chl( k ), l, mid( l, r )
#define RIGHT( k, l, r ) chr( k ), mid( l, r ), r
// セグメント木による Range (Minimum|Maximum) Query
template < typename T = int, typename F = std::less< T >,
T identity = std::is_same< F, std::less< T > >::value ? std::numeric_limits< T >::max() : std::numeric_limits< T >::min(),
typename = typename std::enable_if< std::is_same< F, std::less< T > >::value || std::is_same< F, std::greater< T > >::value >::type >
class RangeMQuery
{
private:
const int N;
std::vector< T > data;
F func;
public:
RangeMQuery( const int n ) :
N( n ), data( N * 4 )
{
return;
}
RangeMQuery( const std::vector< T > &src ) :
N( src.size() ), data( N * 4 )
{
init( src, 0, 0, N );
return;
}
void update( const int p, const T x )
{
return update( p, x, 0, 0, N );
}
T query( const int a, const int b ) const
{
return query( a, b, 0, 0, N );
}
private:
void init( const vector< T > &src, const int k, const int l, const int r )
{
if ( l + 1 == r )
{
data[k] = src[l];
return;
}
init( src, LEFT( k, l, r ) );
init( src, RIGHT( k, l, r ) );
data[k] = std::min( data[ chl( k ) ], data[ chr( k ) ], func );
return;
}
void update( const int p, const T x, const int k, const int l, const int r )
{
if ( p < l || r <= p )
{
return;
}
if ( l + 1 == r && p == l )
{
data[k] = x;
return;
}
update( p, x, chl( k ), l, mid( l, r ) );
update( p, x, chr( k ), mid( l, r ), r );
data[k] = std::min( data[ chl( k ) ], data[ chr( k ) ], func );
return;
}
T query( const int a, const int b, const int k, const int l, const int r ) const
{
if ( b <= l || r <= a )
{
return identity;
}
else if ( a <= l && r <= b )
{
return data[k];
}
else
{
return std::min( query( a, b, chl( k ), l, mid( l, r ) ), query( a, b, chr( k ), mid( l, r ), r ), func );
}
}
};
// RangeMQuery< comp = less, identity element = inf >( N )
// RangeMQuery< comp = less, identity element = inf >( VT src )
// update( pos, x )
// query( [ a, b ) )
int main()
{
cin.tie( 0 );
ios::sync_with_stdio( false );
cout << setprecision( 12 ) << fixed;
int N, M, K;
cin >> N >> M >> K;
VI A( N );
cin >> A;
RangeMQuery< int, greater< int > > rmq( A );
const LL sodd = LL( K / 2 + 1 ) * ( K / 2 + 1 );
const LL seven = LL( K / 2 ) * ( K / 2 + 1 );
LL res = 0;
REP( i, N - 1 )
{
const int j = min( N, i + M + 1 );
const int a = A[i];
const int b = rmq.query( i + 1, j );
chmax( res, a * sodd + b * seven );
chmax( res, b * sodd + a * seven );
}
cout << res << endl;
return 0;
}