#include <fstream>

using namespace std;
ifstream cin("deque.in");
ofstream cout("deque.out");
#define ll long long
int v[5000001],dq[5000001];
int main()
{
    int n,k,st,dr,i;
    ll rez=0;
    cin>>n>>k;
    st=1;
    dr=0;
    for(i=1;i<=n;i++)
    {
        cin>>v[i];
        if(dq[st]<=i-k)
            st++;
        while(dr>=st && v[dq[dr]]>v[i])
            dr--;
        dr++;
        dq[dr]=i;
        if(i>=k)
            rez+=v[dq[st]];
    }
    cout<<rez;
    return 0;
}