#include <fstream>
#include <deque>
using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
int N,K;
deque < pair<int,int > > deq;
int main()
{
    int mn, x;
    long long sum=0;
    cin>>N>>K;
    mn=1e9;
    for(int i=1; i<=N; ++i)
    {
        mn=0;
        cin>>x;
        while(!deq.empty() &&(deq.back()).first>x)
            deq.pop_back();
        deq.push_back({x,i});
        while(!deq.empty() && i-(deq.front()).second+1>K)
            deq.pop_front();
        if(deq.empty())
            cout<<"aiurea"<<'\n';
        else if(i>=K) mn=deq.front().first;
        sum=sum+mn;
    }
    cout<<sum<<'\n';
    return 0;
}