#! ruby
# yukicoder My Practice
# author: Leonardone @ NEETSDKASU

def gs() gets.chomp end
def gi() gets.to_i end
def gss() gets.chomp.split end
def gis() gss.map(&:to_i) end
def nmapf(n,f) n.times.map{ __send__ f } end
def arr2d(h,w,v=0) h.times.map{[v] * w} end
def ngs(n) nmapf n,:gs end
def ngi(n) nmapf n,:gi end
def ngss(n) nmapf n,:gss end
def ngis(n) nmapf n,:gis end
def for2p(hr,wr,&pr) hr.each{|i|wr.each{|j|pr.call(i,j)}} end

N, M = gis
W = gis

if M < 2
    puts 0
    exit
end

z = [true] * N

ans = W.inject(:+)

if N == M
    puts ans
    exit
end

if N - M == 1
    puts (ans - W.rotate(-1).zip(W).map{|x,y|x+y}.min)
    exit
end

if M == 2
    puts [W.max, 0].max
    exit
end