#include <cstdio>
#include <deque>
using namespace std;
//ifstream f("deque.in");
//ofstream g("deque.out");
long long s;
int n,i,k,a[5000005];
deque<int> d;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
    {
        scanf("%d",&a[i]);
        while(!d.empty()&&a[d.back()]>=a[i]) d.pop_back();
        d.push_back(i);
        if(i-d.front()==k) d.pop_front();
        if(i>=k) s+=a[d.front()];
    }
    printf("%lld",s);
    return 0;
}