#include <iostream>
#include <cstdio>
#include <deque>
using namespace std;
int n,k,vCit[5000005];
deque <int> aux;
void citire()
{
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++)
        scanf("%d",&vCit[i]);
}
void solve()
{
    long long sum=0;
    for(int i=1;i<=n;i++)
    {
        while(!aux.empty()&&vCit[aux.back()]>=vCit[i])
        {
            aux.pop_back();
        }
        aux.push_back(i);
        if(aux.front()<i-k+1)
            aux.pop_front();
        if(i>=k)
            sum+=vCit[aux.front()];
    }
    printf("%lld",sum);
}
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    citire();
    solve();
    return 0;
}