#include <cstdio>
#include <deque>

using namespace std;
deque<int> Q;
int N,K,v[5000005];
long long mini;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);

    scanf("%d%d",&N,&K);
    int x,pz = 0;
    for(int i = 1; i <= N; ++i)
        scanf("%d",&v[i]);
    for(int i = 1; i <= N; ++i)
    {
        while(!Q.empty() && v[Q.back()] > v[i])
            Q.pop_back();
        Q.push_back(i);
        if( Q.front() <= i - K )
                Q.pop_front();
        if(i >= K)
            mini += v[Q.front()];
    }
    printf("%lld\n",mini);

    return 0;
}