n,s = map(int,(input().split(" ")))
ls = []
new_ls = []
t = 0
sum = 0
for i in range(n):
    s = int(input())
    ls.append(s)
for j in range(len(ls)):
    if len(ls) % s == 0:
        break
    else:
        ls.append(0)
time = len(ls) // s
for j in range(time):
    sum = 0
    for ss in range(s):
        sum = sum + ls[j*s+ss]
    new_ls.append(sum)
print(min(new_ls),end="")