#include <fstream>

using namespace std;
const int MAXN = 5000001;

ifstream f("deque.in");
ofstream g("deque.out");

int A[MAXN], N, K;
long long sMin = 0;
int D[MAXN],
p = 1, u = 0;

void calcul()
{
    for(int i = 1; i <= N; i++)
    {
        while(p <= u && A[i] <= A[D[u]]) u--;
        D[++u] = i;
        if(i >= K)
        {
            if(D[p] == i - K) p++;
            sMin += A[D[p]];
        }
    }
}

int main()
{
    f >> N >> K;
    for(int i = 1; i <= N; i++)
        f >> A[i];
    calcul();
    g << sMin;
    f.close();
    g.close();
    return 0;
}