using System;
using System.Linq;
using System.Linq.Expressions;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using System.Numerics;
using Number = System.Int64;
namespace Program
{
public class Solver
{
public void Solve()
{
var n = sc.Integer();
var m = sc.Integer();
var k = sc.Integer();
var seg = Enumerate(k + 1, x => new RMQSegmentTree(n + 1));
seg[0].Update(0, 0);
var a = new int[n + 1];
for (int i = 1; i <= n; i++)
a[i] = sc.Integer();
for (int i = 1; i <= k; i++)
for (int j = 1; j <= n; j++)
{
var max = seg[i - 1].Query(Math.Max(0, j - m), j);
seg[i].Update(j, max + 1L * i * a[j]);
}
IO.Printer.Out.WriteLine(seg[k].Query(0, n + 1));
}
public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
}
}
#region main
static class Ex
{
static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
static public void Main()
{
var solver = new Program.Solver();
solver.Solve();
Program.IO.Printer.Out.Flush();
}
}
#endregion
#region Ex
namespace Program.IO
{
using System.IO;
using System.Text;
using System.Globalization;
public class Printer: StreamWriter
{
static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
public static Printer Out { get; set; }
public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
}
public class StreamScanner
{
public StreamScanner(Stream stream) { str = stream; }
public readonly Stream str;
private readonly byte[] buf = new byte[1024];
private int len, ptr;
public bool isEof = false;
public bool IsEndOfStream { get { return isEof; } }
private byte read()
{
if (isEof) return 0;
if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
return buf[ptr++];
}
public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }
public string Scan()
{
var sb = new StringBuilder();
for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
sb.Append(b);
return sb.ToString();
}
public string ScanLine()
{
var sb = new StringBuilder();
for (var b = Char(); b != '\n'; b = (char)read())
if (b == 0) break;
else if (b != '\r') sb.Append(b);
return sb.ToString();
}
public long Long()
{
if (isEof) return long.MinValue;
long ret = 0; byte b = 0; var ng = false;
do b = read();
while (b != 0 && b != '-' && (b < '0' || '9' < b));
if (b == 0) return long.MinValue;
if (b == '-') { ng = true; b = read(); }
for (; true; b = read())
{
if (b < '0' || '9' < b)
return ng ? -ret : ret;
else ret = ret * 10 + b - '0';
}
}
public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
private T[] enumerate<T>(int n, Func<T> f)
{
var a = new T[n];
for (int i = 0; i < n; ++i) a[i] = f();
return a;
}
public char[] Char(int n) { return enumerate(n, Char); }
public string[] Scan(int n) { return enumerate(n, Scan); }
public double[] Double(int n) { return enumerate(n, Double); }
public int[] Integer(int n) { return enumerate(n, Integer); }
public long[] Long(int n) { return enumerate(n, Long); }
}
}
#endregion
#region RMQ Segment Tree
public class RMQSegmentTree
{
const Number ZERO = -1;
int n;
Number[] data;
public RMQSegmentTree(int size)
{
n = 1;
while (n < size)
n <<= 1;
data = new Number[n << 1];
for (int i = 0; i < data.Length; i++)
data[i] = ZERO;
}
public void Update(int k, Number v)
{
k += n;
data[k] = v;
k >>= 1;
while (k > 0)
{
data[k] = merge(data[k << 1], data[(k << 1) + 1]);
k >>= 1;
}
}
public Number Query(int a, int b) { return query(a, b, 1, 0, n); }
private Number query(int a, int b, int k, int l, int r)
{
if (r <= a || b <= l)
return ZERO;
if (a <= l && r <= b)
return data[k];
else
{
var vl = query(a, b, k << 1, l, (l + r) >> 1);
var vr = query(a, b, (k << 1) + 1, (l + r) >> 1, r);
return merge(vl, vr);
}
}
Number merge(Number l, Number r)
{
return Math.Max(l, r);
}
public Number[] Items
{
get
{
var ret = new Number[n];
for (int i = 0; i < n; i++)
ret[i] = data[i + n];
return ret;
}
}
}
#endregion