#include<fstream>
#include<deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
deque <int> dq;
#define int long long
int n,k,s,v[5000005];
signed main(){
    cin>>n>>k;
    for(int i=1;i<=n;++i)
        cin>>v[i];
    for(int i=1;i<=n;++i){
        while(!dq.empty() && v[i]<=v[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if(!dq.empty() && dq.front()==i-k)
            dq.pop_front();
        if(i>=k)
            s+=v[dq.front()];
    }
    cout<<s;
}