#include <fstream>
#include <deque>
#define NM 5000006
#define ll long long
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
ll n,k,i,s;
ll a[NM];
deque < ll > d;
int main()
{
    f>>n>>k;
    for(i=1;i<=n;i++){
        f>>a[i];
        while(!d.empty()&&a[d.back()]>=a[i]) d.pop_back();
        d.push_back(i);
        if(d.front()==i-k) d.pop_front();
        if(i>=k)  s+=a[d.front()];
    }
    g<<s<<'\n';
    return 0;
}