python

n, m = map(int, input().split())
w = list(map(int, input().split()))

if n <= m:
print(max(w))
else:
# 初始化前m个水龙头
taps = wm
remaining = w[m:]
time = 0

while True:
    # 找出当前所有水龙头中的最小值
    min_time = min(taps)
    time += min_time
    
    # 更新所有水龙头的剩余时间
    taps = [t - min_time for t in taps]
    
    # 处理所有刚好完成的水龙头
    for i in range(m):
        if taps[i] == 0:
            if remaining:
                taps[i] = remaining.pop(0)
            else:
                taps[i] = float('inf')  # 标记为已完成
    
    # 检查是否所有同学都完成了
    if not remaining and all(t == float('inf') for t in taps):
        break

print(time)