#include <fstream>

using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int v[5000001],c[5000001];
int main()
{
    int n,i1=1,i2=0,i,k;
    long long rez=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>v[i];
    for(i=1;i<=k-1;i++)
    {
        while(i2>=i1&&v[c[i2]]>v[i])
            i2--;
        i2++;
        c[i2]=i;
    }
    for(i=k;i<=n;i++)
    {
        if(c[i1]<i-k+1)
            i1++;
        while(i2>=i1&&v[c[i2]]>v[i])
            i2--;
        i2++;
        c[i2]=i;
        rez+=1LL*v[c[i1]];
    }
    cout<<rez;
    return 0;
}