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) for i, v in enumerate(vs)]
    vis.sort()
    cum = sum(ws)
    for i in range(n - m):
        v, i = heapq.heappop(vis)
        while vs[i] != v:
            v, i = heapq.heappop(vis)
        cum -= v
        vs[i] = float('inf')
        j = (i + 1) % n
        k = (i - 1) % n
        vs[j] -= ws[i]
        vs[k] -= ws[k]
        heapq.heappush(vis, (vs[j], j))
        heapq.heappush(vis, (vs[k], k))
    return cum

print(solve(n, m, ws))