#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for (int i=0; i<n; i++)
#define pb push_back
typedef long long ll;

ll op(ll x, ll y) { return min(x, y); }
ll e() { return 2000000000000000000ll; }

int main() {
    cin.tie(0); ios::sync_with_stdio(false);
    
    int N, K; cin >> N >> K;
    ll A[N]; rep(i, N) cin >> A[i];
    
    segtree<ll, op, e> st(N);
    rep(i, K) st.set(i, A[i]);
    for (int i=K; i<N; i++) st.set(i, st.prod(i-K, i)+A[i]);
    
    ll S = 0ll;
    rep(i, N) S += A[i];
    ll ans = S-st.prod(N-K, N);
    cout << ans << endl;
}