#include<fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
deque <int> d;
int v[5000001];
int main(){
int n,k,i;
long long s=0;
cin>>n>>k;
for(i=1;i<=n;i++){
    cin>>v[i];
    while(!d.empty()&&v[i]<v[d.back()])
        d.pop_back();
    d.push_back(i);
    if(i>=k){
        s+=v[d.front()];
        if(!d.empty()&&d.front()+k-1<=i)
            d.pop_front();
    }
}
cout<<s;
return 0;
}