package main

import (
	"bufio"
	"fmt"
	"math/bits"
	"os"
)

func main() {
	// https://yukicoder.me/problems/no/1097
	const INF int = int(1e18)
	const MOD int = 998244353

	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var n, m, l int
	fmt.Fscan(in, &n, &m, &l)
	nums := make([]int, n)
	for i := 0; i < n; i++ {
		fmt.Fscan(in, &nums[i])
	}

	db := NewDoubling(n, 1e15)
	for i := 0; i < n; i++ {
		j := (i + l) % n
		db.Add(i, j, nums[j])
	}
	db.Build()

	res := -INF
	for i := 0; i < n; i++ {
		s0 := i
		s1 := l/n*n + i
		for s0 >= l {
			s0 -= n
		}
		for s1 >= l {
			s1 -= n
		}
		a0 := (n*m - 1 - s0) / l
		a1 := (n*m - 1 - s1) / l
		if s0 >= 0 {
			_, v := db.Jump(i, a0)
			res = max(res, v+nums[i])
		}
		if s1 >= 0 {
			_, v := db.Jump(i, a1)
			res = max(res, v+nums[i])
		}
	}

	fmt.Fprintln(out, res)
}

func max(a, b int) int {
	if a > b {
		return a
	}
	return b
}

type E = int

// monoidAdd
func (*Doubling) e() E          { return 0 }
func (*Doubling) op(e1, e2 E) E { return e1 + e2 }

type Doubling struct {
	n          int
	log        int
	isPrepared bool
	to         [][]int
	dp         [][]E
}

func NewDoubling(n, maxStep int) *Doubling {
	res := &Doubling{}
	res.n = n
	res.log = bits.Len(uint(maxStep))
	res.to = make([][]int, res.log)
	res.dp = make([][]E, res.log)
	for i := 0; i < res.log; i++ {
		res.to[i] = make([]int, n)
		res.dp[i] = make([]E, n)
		for j := 0; j < n; j++ {
			res.to[i][j] = -1
			res.dp[i][j] = res.e()
		}
	}
	return res
}

// 初始状态(leaves):从 `from` 状态到 `to` 状态，状态的值变为 `value`.
//  0 <= from, to < n
func (d *Doubling) Add(from, to int, value E) {
	if d.isPrepared {
		panic("Doubling is prepared")
	}
	if to < -1 || to >= d.n {
		panic("to is out of range")
	}

	d.to[0][from] = to
	d.dp[0][from] = value
}

func (d *Doubling) Build() {
	if d.isPrepared {
		panic("Doubling is prepared")
	}

	d.isPrepared = true
	for k := 0; k < d.log-1; k++ {
		for v := 0; v < d.n; v++ {
			w := d.to[k][v]
			if w == -1 {
				d.to[k+1][v] = -1
				d.dp[k+1][v] = d.dp[k][v]
				continue
			}
			d.to[k+1][v] = d.to[k][w]
			d.dp[k+1][v] = d.op(d.dp[k][v], d.dp[k][w])
		}
	}
}

func (d *Doubling) Jump(from, step int) (to int, res E) {
	if !d.isPrepared {
		panic("Doubling is not prepared")
	}
	if step >= 1<<d.log {
		panic("step is over max step")
	}

	res = d.e()
	to = from
	for k := 0; k < d.log; k++ {
		if to == -1 {
			break
		}

		if step&(1<<k) != 0 {
			res = d.op(res, d.dp[k][to])
			to = d.to[k][to]
		}
	}
	return
}

func (d *Doubling) MaxStep(from int, check func(e E) bool) int {
	if !d.isPrepared {
		panic("Doubling is not prepared")
	}

	res := d.e()
	step := 0
	if !check(res) {
		return 0
	}

	for k := d.log - 1; k >= 0; k-- {
		to := d.to[k][from]
		next := d.op(res, d.dp[k][from])
		if check(next) {
			step |= 1 << k
			from = to
			res = next
		}
	}

	return step
}