#include <atcoder/all>
using namespace std;
using ll = long long;

ll op(ll lhs, ll rhs){return min(lhs, rhs);}
ll e(){return 1ll << 60;}

int main(){
    int n, k, v;
    cin >> n >> k;
    atcoder::segtree<ll, op, e> seg(vector<ll>(n + k, 0));
    ll s = 0;
    for(int i = k; i < n + k; i++){
        cin >> v;
        s += v;
        seg.set(i, v + seg.prod(i - k, i));
    }
    cout << s - seg.prod(n, n + k) << '\n';
}