#include <bits/stdc++.h>
using namespace std;
long long n,k,i,ma,df,v[5000010],mi,s;
deque<long long>dm;
int main()
{
    freopen("deque.in","r",stdin);
    ofstream g ("deque.out");
    scanf("%lld%lld",&n,&k);
    for(i=1; i<=n; ++i)
        scanf("%lld",&v[i]);
        mi=10000001;
    for(i=1; i<=n; ++i)
    {
        while(!dm.empty()&&v[i]<v[dm.back()])dm.pop_back();
        dm.push_back(i);
        if(i-dm.front()==k)dm.pop_front();
        if(i>=k)s+=1LL*v[dm.front()];
    }
    g<<s;
    return 0;
}