#include <cstdio>
#include <deque>
using namespace std;

deque < int > Deque;
int V[5000001];
int n,k;
long long Smin;

int main(){

    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
        for(register int i=1;i<=n;++i)
            scanf("%d",&V[i]);
Deque.push_back(1);

        for(register int i=2;i<=n;++i){
            while(!Deque.empty() && V[Deque.back()] >= V[i])
                Deque.pop_back();
                Deque.push_back(i);

          if(Deque.front() == i-k)
            Deque.pop_front();

          if(i>=k)
                Smin+=V[Deque.front()];
}

printf("%lld",Smin);
return 0;
}