#include <fstream>
#include <deque>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
long long i,a[5000002],n,k;
deque <int> d;
long long s;
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(i-d.front()>=k)
        d.pop_front();
    if(i>=k) s+=a[d.front()];
}
g<<s;


    return 0;
}