#include <fstream>

#define Nmax 5000100

using namespace std;


int N, K, A[Nmax], Deque[Nmax];
long long Answer;

int main() {

    int i, Left, Right;
    ifstream in("deque.in");
    ofstream out("deque.out");

    in >> N >> K;
    Left = 1;
    Right = 0;
    for(i = 1; i <= N; i++) {

        for(in >> A[i]; Left <= Right && A[Deque[Right]] > A[i]; Right--);

        Deque[++Right] = i;

        if(Deque[Left] <= i - K)
            ++Left;

        if(i >= K)
            Answer += A[Deque[Left]];
    }

    out << Answer << '\n';

    in.close();
    out.close();

    return 0;
}