#include <fstream>
#include <deque>
#define NMAX 5000010
#define intt long long
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
intt n, v[NMAX],sol,k;
deque <int> Q;
int main()
{
    f >> n >> k;
    for(int i = 1; i <= n; ++i)
        f >> v[i];
    for(int i = 1; i <=n; ++i)
    {
        while(!Q.empty() && v[Q.back()] > v[i]) Q.pop_back();
        Q.push_back(i);
        if(k == i - Q.front()) Q.pop_front();
        if(i >= k) sol += v[Q.front()];

    }
    g<< sol;
    f.close();
    g.close();
    return 0;
}