#pragma comment(linker, "/stack:200000000")
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <bits/stdc++.h>
#define MOD 1000000007

using namespace std;

typedef unsigned long long ll;
typedef pair< int , int > PII;

int n, m;

struct SegTree{
	struct Node{
		ll mn;
	};

	vector < Node > T;

	void Init(int node, int st, int dr, ll a[]){
		if (st == dr){
			T[node].mn = a[st];
		}else{
			int mid = (st + dr) >> 1;
			Init(node << 1, st, mid, a);
			Init(node << 1 | 1, mid + 1, dr, a);
			T[node].mn = Pull(T[node << 1 | 1], T[node << 1]);
		}
	}

	ll Pull(Node A, Node B){
		return min(A.mn, B.mn);
	}

	SegTree(ll a[], int n) : T(4 * n + 200) {
		Init(1, 1, n, a);
	}

	ll Query(int node, int st, int dr, int le, int ri){
		if (st > ri || dr < le){
			return LLONG_MAX;
		}

		if (st >= le && dr <= ri){
			return T[node].mn;
		}

		int mid = (st + dr) >> 1;
		ll A = Query(node << 1, st, mid, le, ri);
		ll B = Query(node << 1 | 1, mid + 1, dr, le, ri);
		return min(A, B);
	}
};

ll dp[100100], sum[100100], a[100100];

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n >> m;

	for (int i = 1; i <= n; i++){
		cin >> a[i];
		sum[i] = a[i] + sum[i - 1];
		dp[i] = LLONG_MAX;
	}

	SegTree tree(a, n);

	for (int i = 1; i <= n; i++){
		dp[i] = dp[i - 1] + a[i];
		if (i >= m) dp[i] = min(dp[i], dp[i - m] + sum[i] - sum[i - m] + tree.Query(1, 1, n, i - m + 1, i));
	}

	cout << dp[n];
	return 0;
}