#include <iostream>
#include <fstream>

using namespace std;
const int N=5e6;
int dq[N+1],v[N+1];
int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    int p=0,u=0;
    int k,i,n;
    long long ans=0;
    cin>>n>>k;
    for(i=1;i<=n;i++)
        cin>>v[i];
    for(i=1;i<=n;i++)
        {
        while(p && u && p<=u && i-dq[p]>=k)
            ++p;
        while(p && u && p<=u && v[dq[u]]>=v[i])
            --u;
        dq[++u]=i;
        if(p ==0)
            p=1;
        if(i>=k) {
            ans +=v[dq[p]];
        }
    }
    cout<<ans;
    return 0;
}