# include <cstdio>
# include <deque>
# define pb push_back
# define popb pop_back
# define popf pop_front
# define MAXN 5000001

using namespace std;

int N,K,i,x,S;
int a[MAXN];
deque <int> h;
deque <int> :: iterator it;

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d %d\n", &N, &K);
    for(i=1; i<=N; ++i) scanf("%d\n", &a[i]);
    h.pb(1);
    for(i=2; i<=N; ++i)
    {
        it=h.end();
        it--;
        while(a[(*it)]>a[i])
        {
            h.popb();
            it=h.end();
            it--;
        }
        h.pb(i);
        it=h.begin();
        while((*it)<=i-K)
        {
            h.popf();
            it=h.begin();
        }
        if(i>=K) S+=a[*(h.begin())];
    }
    printf("%d\n", S);
    fclose(stdin);
    fclose(stdout);
    return 0;
}