#include <cstdio>

using namespace std;

int v[5000002];
int stiva[5000002];

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k,st,dr;
    long long sol=0;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++) scanf("%d",&v[i]);
    st=1;dr=0;
    for(int i=1;i<=n;i++)
    {
        while(st<=dr && v[stiva[dr]]>=v[i]) dr--;
        stiva[++dr]=i;
        if(stiva[st]<i-k+1) st++;
        if(i>=k) sol+=v[stiva[st]];

    }
    /*for(int i=1;i<=n;i++)
    {
        while(!stiva.empty() && v[stiva.back]>=v[i]) stiva.pop-back();
        stiva.push-back(i);
        if(stiva.front()<i-k+1) stiva.pop_front();
        sol=v[stiva.front()];
    }*/
    printf("%lld",sol);
    return 0;
}