#include <iostream>
#include <fstream>

using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");
const int N=5000010;
long long n,k,v[N],st,dr;
long sum,d[N];
int main()
{
f>>n>>k;
st=0;
dr=-1;
for(int i=0; i<n; i++)
{
    f>>v[i];
    if(st<=dr && d[st]==i-k)
    {
        st++;
    }
    while(st<=dr && v[i]<=v[d[dr]])
    {
        dr--;
    }
    d[++dr]=i;
    if(i>=k-1)
    {
        sum+=v[d[st]];
    }
}
g<<sum;
    return 0;
}