#include <stdio.h>
typedef long long int lld;
lld costs[10001];
lld preCompute[10001];
lld costToTurnOff(int N, int K) {
   int k;
   lld cost, startCost;
   if (N <= 0) { return 0; }
   if (preCompute[N] >= 0) { return preCompute[N]; }

   startCost = costs[N] + costToTurnOff(N-K-1,K);
   for (k=N-K; k < N; ++k) {
      if (k <= 0) { continue; }
      cost = costs[k] + costToTurnOff(k-K-1,K);
      if (cost < startCost) { startCost = cost; }
   }
   return (preCompute[N] = startCost);
}


int main() {
   int n,k,N,K;
   if (2 != scanf("%d %d", &N, &K)) { return 1; }
   for (n=0; n <= N; ++n) {
      preCompute[n] = -1; 
   }
   for (n=1; n <= N; ++n) {
      scanf("%lld", costs+n);
   }
   printf("%lld\n", costToTurnOff(N,K));




}