import heapq
n, m = map(int, input().split())
ws = list(map(int, input().split()))

def solve(n, m, ws):
    vs = [a + b for a, b in zip(ws, [ws[-1]] + ws[:-1])]
    vis = [(v, i, 2) for i, v in enumerate(vs)]
    edges = [2] * n
    e_exists = [True] * n
    v_exists = [True] * n
    vis.sort()
    cum = sum(ws)
    for _ in range(n - m):
        v, i, n_edges = heapq.heappop(vis)
        while edges[i] != n_edges or not v_exists[i]:
            v, i, n_edges = heapq.heappop(vis)
        vs[i] = 0
        cum -= v
        edges[i] = 0
        v_exists[i] = False
        j = (i + 1) % n
        k = (i - 1) % n
        if e_exists[i]:
            e_exists[i] = False
            vs[j] -= ws[i]
            ws[i] = 0
            edges[j] -= 1
            heapq.heappush(vis, (vs[j], j, edges[j]))
        if e_exists[k]:
            e_exists[k] = False
            vs[k] -= ws[k]
            ws[k] = 0
            edges[k] -= 1
            heapq.heappush(vis, (vs[k], k, edges[k]))
    return cum

print(solve(n, m, ws))