#include <iostream>
#include <fstream>
using namespace std;

int d[5000001], v[5000001];

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");

int n, k, u=1, i, p=1;
long s=0;

cin>>n>>k;

for(i=1;i<=n;i++)
    cin>>v[i];

d[p]=1;

for(i=2;i<=n;i++)
{
    while(u>=p && v[i]<=v[d[u]])
        u--;
    d[++u] = i;

    if(d[p]==i-k)
        p++;

    if(i>=k)
        s+=v[d[p]];
}
cout<<s;
    return 0;
}