n = int(input())
arr = [0]+list(map(int, input().split()))
n+=1
mi, ma = map(int, input().split())
dp = [0]*(n)
from collections import deque
stack = deque()
for i in range(mi, n):
    while stack and stack[-1] < dp[i-mi]:
        stack.pop()
    stack.append(dp[i-mi])
    if i >= ma:
        if stack and stack[0] == dp[i-ma]:
            stack.popleft()
    dp[i] = stack[0]+arr[i]

print(dp[-1] or -1)