#include<iostream>
#include<fstream>
#include<deque>
using namespace std;
struct ij
{
    int val;
    int pos;
};

deque <ij> st;
int n, v[1001], mi = INT_MAX, s, I, k, i;
int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d%d", &n, &k);
    for( i = 1; i <= n; i++)
        scanf("%d", &v[i]);
    for( i = 1; i <= k; i++)
    {
        if(v[i] <= mi)
            mi = min(mi, v[i]), I = i;

        while(!st.empty() && st.front().val > v[i])
            st.pop_front();
        st.push_front({v[i], i});
    }
    s += mi;
    for( i = k + 1; i <= n; i++)
    {
        while(!st.empty() && st.back().pos < i - k + 1)
            st.pop_back();
        while(!st.empty() && st.front().val > v[i])
            st.pop_front();
        st.push_front({v[i], i});
        s += st.back().val;
    }
    printf("%d", s);
}