n, m, k = map(int, input().split())

a = [int(input()) for _ in range(n)]

count = 0
counts = [0 for _ in range(n)]
nextZero = [i - 1 for i in range(n)]


for start in range(-m + 1, n):
    index = min(start + m - 1, n - 1)
    # print("index", index, count)
    prev = -1

    while k - count > 0 and index >= 0 and index >= start:
        # print(a[index], counts[index], k, count)
        add = min(a[index] - counts[index], k - count)
        counts[index] += add
        count += add

        if counts[index] == a[index]:
            if prev >= 0:
                nextZero[prev] = index + 1
            prev = index
            index = nextZero[index]
    # print("-"*20)
    # print(counts)
    # print(nextZero)

    if start >= 0:
        count -= counts[start]


print(sum(counts))