#include <bits/stdc++.h>

using namespace std;

const int N = 20004, K = 1003;
long long dp[N][K];
int c[N];

int main() {
  int n, k;
  scanf("%d %d", &n, &k);
  for (int i = 0; i < n; ++i) {
    scanf("%d", c + i);
  }
  for (int j = 1; j <= k; ++j) {
    dp[n][j] = 1e18;
  }
  for (int i = n - 1; i >= 0; --i) {
    for (int j = 0; j <= k; ++j) {
      dp[i][j] = dp[i + k + 1][0] + c[i];
      if (j < k)
        dp[i][j] = min(dp[i][j], dp[i + 1][j + 1]);
    }
  }
  printf("%lld\n", dp[0][0]);
  return 0;
}