// Meysam Aghighi
// Comments: 
#include <bits/stdc++.h>
using namespace std;

int main() { 
	int n,k;
	cin >> n >> k;
	long long c[n];
	vector<long long> a(n,1e10); 
	for (int i=0;i<n;i++) cin >> c[i];
	a[0] = c[0];
	for (int i=1;i<n;i++){
		// set a[i]
		for (int j=max(0,i-k);j<=i;j++){			
			if (j-k-1>=0) a[i] = min(a[i],a[j-k-1]+c[j]);
			else a[i] = min(a[i],c[j]);				
		}
		// cout << i << " " << a[i] << endl;
	}
	cout << a[n-1] << endl;
    return 0;
}