#include <cstdio>
#include <queue>
using namespace std;
const int Nmax = 5000001;
int n, k, A[Nmax];
deque <int> D;
long long Sum;
int main()
{   freopen("deque.in", "r", stdin); freopen("deque.out", "w", stdout);
    scanf("%d %d ", &n, &k);
    for(int i=1; i<=n; ++i) scanf("%d ", &A[i]);
    for(int i=1; i<=n; ++i)
    {   while(!D.empty() &&  A[i] <= A[D.back()]) D.pop_back();
        D.push_back(i);
        if(D.front() == i-k) D.pop_front();
        if(i >= k) Sum += A[D.front()];
    }
    printf("%lld\n", Sum);
    return 0;
}