#include<cstdio>
#include<fstream>
#include<deque>
using namespace std;
FILE *f=fopen("deque.in","r");
ofstream g("deque.out");
const int NMAX=5000002;
deque<int> d;
int v[NMAX];
int main()
{
    int n,k,i;
    long long sol=0;
    fscanf(f,"%d%d",&n,&k);
    for(i=1;i<=n;i++)
        fscanf(f,"%d",&v[i]);
    for(i=1;i<=n;i++)
    {
        while(!d.empty()&&v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(d.back()-d.front()==k)
            d.pop_front();
        if(d.back()>=k)
            sol+=v[d.front()];
    }
    g<<sol;
    return 0;
}