#include <fstream>

#define nMax 5000001
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n, k;
int deque[nMax], v[nMax];
long long Sol;
void read()
{
    fin>>n>>k;

    for(int i=1;i<=n;i++)
        fin>>v[i];
}
void solve()
{
    int st=1, dr=0;

    for(int i=1;i<=n;i++)
    {
        if(k<=i-deque[st])
            st++;

        while(dr>=st && v[i]<=v[deque[dr]])
            dr--;

        deque[++dr]=i;

        if(i>=k)
            Sol+=v[deque[st]];
    }

    fout<<Sol;
}
int main()
{
    read();
    solve();
    return 0;
}