#include <fstream>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
int p ,i,nr,v[5000001],q[5000001],k,u,n;
long long s;
int main()
{f>>n>>k;

    p=1;u=1;
    f>>v[1];
    q[1]=1;
    for(i=2;i<=n;i++){
        f>>v[i];
while(v[i]<=v[q[u]]&&p<=u){
    u--;
    }
    u++;
    q[u]=i;
while(i-nr>k&&nr<i)
{
    nr++;
    if(nr==q[p])
        p++;
}
if(i-nr==k)
    s=s+v[q[p]];
    }
g<<s;

    return 0;
}