#include<iostream>
#include<deque>
#include<fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
deque<int> D;
int A[5000001];
int n,k,i;
long long S;
int main()
{f>>n>>k;
for(i=1;i<=n;i++)
{f>>A[i];
while(!D.empty()&&A[i]<=A[D.back()])D.pop_back();
D.push_back(i);
if(k==i-D.front())D.pop_front();
if(i>=k)S+=A[D.front()];
}
g<<S;
f.close();
g.close();
return 0;



}