#include<bits/stdc++.h>
using namespace std;
using LL = long long;
using ULL = unsigned long long;
#define rep(i,n) for(int i=0; i<(n); i++)

int N, K;
LL A[200000];

int main() {
    cin >> N >> K;
    rep(i, N) cin >> A[i];

    LL ans = A[K - 1];
    priority_queue<LL> Q;
    LL tmp = 0;
    for (int i = 2; i * K <= N; i++) {
        for (int j = (i - 1) * K - 1; j < i * K - 1; j++) {
            tmp += A[j];
            Q.push(A[j]);
        }
        rep(i, K - 1) {
            tmp -= Q.top(); Q.pop();
        }
        ans = min(ans, tmp + A[i * K - 1]);
    }

    cout << ans << endl;

    return 0;
}