#include<cstdio>
#include<deque>
using namespace std;
deque<int> coada;
int n,m,i,j,k,v[5000001];
long long s;
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",&v[i]);
    while(!coada.empty()&&v[i]<v[coada.back()])
        coada.pop_back();
    coada.push_back(i);
    if(i>=k){
        s+=v[coada.front()];
        if(!coada.empty()&&i-coada.front()+1>=k)
            coada.pop_front();
    }
}
printf("%lld",s);
}