#include <bits/stdc++.h>

using namespace std;

const int N = 1e4;

int n, K;
long long C[N + 1];
const long long INF = (1LL << 60);
long long dp[N + 1003][1003];

long long minCost(int curr, int lastOff) {
    //cout << curr << " " << lastOff << "\n";
	if(curr - K > lastOff + 1) {
		return INF;
	}
    if(curr > n)
        {
        if(lastOff >= n)
            return 0;
        return INF;
    }
	//  if(lastOff >= n)
		//return 0;
	long long& res = dp[curr][lastOff];
	if(res != -1) {
		return res;
	}
	res = INF;

	res = min(C[curr] + minCost(curr + K + 1, curr + K), minCost(curr + 1, lastOff));
	return res;
}

int main(int argc, char const *argv[]){
	// freopen("C:\\Users\\Paramdeep Singh\\Desktop\\input.txt","r",stdin);
	// freopen("C:\\Users\\Paramdeep Singh\\Desktop\\output.txt","w",stdout);

	memset(dp, -1, sizeof(dp));

	scanf("%d %d", &n, &K);
	for(int i = 1; i <= n; i++) {
		scanf("%lld", &C[i]);
	}
    
    // return 0;

	printf("%lld\n", minCost(1,0));
	
	
	return 0;
}