#include <cstdio>
#include <algorithm>
#include <deque>
#define Dim 5000002

using namespace std;
int n, k, i, A[Dim];
deque <int> dq;
long long sol;
void read()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d %d", &n, &k);
    for(i = 1; i <= n; ++ i)
        scanf("%d", &A[i]);

}
void solve()
{
    int i;
    for(i = 1; i <= n; ++ i)
    {
        while(!dq.empty() && A[i] <= A[dq.back()])
            dq.pop_back();
        dq.push_back(i);
        if(dq.front() == i - k)
            dq.pop_front();
        if(i >= k)
            sol += A[dq.front()];

    }
}
void write()
{
    printf("%lld\n", sol);
}
int main()
{
    read();
    solve();
    write();
    return 0;
}