#include <cstdio>
#include <deque>

#define Nmax 5000055

using namespace std;

long long rez = 0;
deque<int> Q;
int N,K,v[Nmax];

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",&v[i]);
        while(!Q.empty() && v[Q.back()] >= v[i])
            Q.pop_back();
        Q.push_back(i);
        while(!Q.empty() && i - Q.front() >= K)
            Q.pop_front();
        if(i >= K)
            rez += v[Q.front()];
    }
    printf("%lld\n",rez);

    return 0;
}