#gpt(一時チャット)
import sys


def solve():
    input = sys.stdin.readline
    N, K, L = map(int, input().split())
    A = list(map(int, input().split()))

    # 切れ目によって区切られる各区間の長さ
    d = [A[0]]
    for i in range(1, N):
        d.append(A[i] - A[i - 1])
    d.append(L - A[-1])

    M = N + 1
    limit = M - K + 1  # 2つの大きい部分列が使ってよい区間数の上限

    def feasible(H: int) -> bool:
        if H <= 0:
            return True

        INF = 10**18

        # pref[i] = d[0..i] の中で、和 >= H となる部分列の最小長
        pref = [INF] * M
        s = 0
        l = 0
        best = INF
        for r in range(M):
            s += d[r]
            while s >= H:
                best = min(best, r - l + 1)
                s -= d[l]
                l += 1
            if r > 0:
                pref[r] = min(pref[r - 1], best)
            else:
                pref[r] = best

        # suf[i] = d[i..M-1] の中で、和 >= H となる部分列の最小長
        suf = [INF] * M
        s = 0
        r = M - 1
        best = INF
        for l in range(M - 1, -1, -1):
            s += d[l]
            while s >= H:
                best = min(best, r - l + 1)
                s -= d[r]
                r -= 1
            if l < M - 1:
                suf[l] = min(suf[l + 1], best)
            else:
                suf[l] = best

        # 左側の部分列と右側の部分列を分けて選ぶ
        for i in range(M - 1):
            if pref[i] + suf[i + 1] <= limit:
                return True
        return False

    lo, hi = 0, L + 1
    while hi - lo > 1:
        mid = (lo + hi) // 2
        if feasible(mid):
            lo = mid
        else:
            hi = mid

    print(lo)


if __name__ == "__main__":
    solve()