#include <bits/stdc++.h>

using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
struct tip{int val; int poz;};
deque<tip> Q;
int x,n,i,k;
long long int suma;

int main()
{fin>>n>>k;
 while(n--)
    {
     i++;
     fin>>x;

     while( !Q.empty() && Q.back().val>= x)
                Q.pop_back();

     Q.push_back({x,i});

     while(!Q.empty() && Q.front().poz<=i-k)
        Q.pop_front();
     if(i>=k)
     suma+=Q.front().val;

    }
 fout<<suma;
    return 0;
}