#include <bits/stdc++.h>
#define ll long int
using namespace std;
deque <ll> q;
const int nmax=1e6;
ll arr[5*nmax+5],n,k;
long long int sum=0;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    ios_base::sync_with_stdio(false);
    cin.tie(0);
    cin>>n>>k;
    for(int i=0;i<n;++i)
        cin>>arr[i];
    int i;
    for(i=0;i<k;++i){
        while((!q.empty()) && arr[i]<=arr[q.back()])
            q.pop_back();
        q.push_back(i);
    }
    for(;i<n;++i){
        sum+=arr[q.front()];
        while((!q.empty()) && q.front()<=i-k)
            q.pop_front();
        while((!q.empty()) && arr[i]<=arr[q.back()])
            q.pop_back();
        q.push_back(i);
    }
    sum+=arr[q.front()];
    cout<<sum;
}