#include <fstream>
#include <list>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int l[5000005];
int v[5000005];
int main()
{
    int n,k,a;
    long long sum=0;
    cin>>n>>k;
    for(int i=1; i<=n; i++)
    {
        cin>>a;
        v[i]=a;
    }
    int i1=1,i2=0;
    for(int i=1; i<=n; i++)
    {
        while(i1<=i2&&v[i]<=v[l[i2]])
            i2--;
        l[++i2]=i;
        if(l[i1]==i-k)
            i1++;
        if(i>=k)
            sum+=v[l[i1]];
    }
    cout<<sum;
    return 0;
}