import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################
def xgcd(a, b):
    x0, y0, x1, y1 = 1, 0, 0, 1
    while b != 0:
        q, a, b = a // b, b, a % b
        x0, x1 = x1, x0 - q * x1
        y0, y1 = y1, y0 - q * y1
    return a, x0, y0

def modinv(a, m):
    g, x, y = xgcd(a, m)
    if g != 1:
        raise Exception('modular inverse does not exist')
    else:
        return x % m
N,M,L = na()
a = na()
from math import gcd
ans = -float("inf")
g = gcd(N, L)
n = N//g
R = L//g
u = modinv(R, n)
for x in range(g):
    z = [0]
    for i in range(n):
        z.append(z[-1] + a[(x + i * L)%N])
    f = R-(-n*M)%R
    l = 0
    r = (n * M - 1) // R + 1
    for i in range(n):
        if i < f:
            ans = max(ans, z[r%n] - z[l%n] + z[-1] * (r//n-l//n))
            #print("< ",l, r,z[r%n] - z[l%n] + z[-1] * (r//n-l//n))
        l += u
        r += u
    l = 0
    r = (n * M - 1) // R 
    for i in range(n):
        i = (R-i-1)//n * n + i
        if i >= f:
            ans = max(ans, z[r%n] - z[l%n] + z[-1] * (r//n-l//n))
            #print(">=",l, r,z[r%n] - z[l%n] + z[-1] * (r//n-l//n))
        l += u
        r += u

print(ans)