#include <stdio.h>

void set_segt (long long *t, int idx, long long val, int size) {
  idx = idx+size-1;
  t[idx] = val;
  
  while (idx > 0) {
    idx = (idx-1)/2;
    if (t[2*idx+1] < t[2*idx+2]) {
      t[idx] = t[2*idx+1];
    } else {
      t[idx] = t[2*idx+2];
    }
  }
  
  return;
}

long long min_segt_rec (long long *t, int a, int b, int k, int l, int r) {
  long long ans = 0LL;
  long long tmp = 0LL;
  
  if (r <= a || b <= l) {
    return 1000000000000000LL;
  }
  
  if (a <= l && r <= b) {
    return t[k];
  }
  
  ans = min_segt_rec(t, a, b, 2*k+1, l, (l+r)/2);
  tmp = min_segt_rec(t, a, b, 2*k+2, (l+r)/2, r);
  
  if (tmp < ans) {
    ans = tmp;
  }
  
  return ans;
}

long long min_segt (long long *t, int a, int b, int size) {
  return min_segt_rec(t, a, b, 0, 0, size);
}

int main () {
  int n = 0;
  int k = 0;
  long long a[200000] = {};
  
  int res = 0;
  
  long long sum = 0LL;
  long long segt[600000] = {};
  
  int size = 1;
  
  res = scanf("%d", &n);
  res = scanf("%d", &k);
  for (int i = 0; i < n; i++) {
    res = scanf("%lld", a+i);
    sum += a[i];
  }
  
  while (size < n+1) {
    size *= 2;
  }
  
  for (int i = 0; i < n; i++) {
    long long val = min_segt(segt, i-k+1, i+1, size);
    set_segt(segt, i+1, val+a[i], size);
  }
  
  printf("%lld\n", sum-min_segt(segt, n-k+1, n+1, size));
  return 0;
}