package contest201002; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStream; import java.io.PrintWriter; import java.util.Arrays; import java.util.InputMismatchException; public class G { InputStream is; PrintWriter out; String INPUT = ""; void solve() { int n = ni(), K = ni(); int[] a = na(n); if(K == 1){ out.println(a[0]); return; } SegmentTreeRMQPos st = new SegmentTreeRMQPos(a); long ans = Long.MAX_VALUE; int[] u = new int[n+1]; for(int i = K-1;i < n;i++){ long can = a[i]; int h = (i+K-2)/(K-1); if((long)K*(h-1)+K-1 >= n)continue; for(int j = h;j >= 2;j--){ int L = Math.max(i+1, K*(j-1)+K-1); int min = st.minx(L, n); can += min; u[j] = st.minpos; st.update(st.minpos, Integer.MAX_VALUE); } ans = Math.min(ans, can); for(int j = 2;j <= h;j++){ st.update(u[j], a[u[j]]); } } out.println(ans); } public static class SegmentTreeRMQPos { public int M, H, N; public int[] st; public int[] pos; public SegmentTreeRMQPos(int n) { N = n; M = Integer.highestOneBit(Math.max(N-1, 1))<<2; H = M>>>1; st = new int[M]; pos = new int[M]; for(int i = 0;i < N;i++)pos[H+i] = i; Arrays.fill(st, 0, M, Integer.MAX_VALUE); for(int i = H-1;i >= 1;i--)propagate(i); } public SegmentTreeRMQPos(int[] a) { N = a.length; M = Integer.highestOneBit(Math.max(N-1, 1))<<2; H = M>>>1; st = new int[M]; pos = new int[M]; for(int i = 0;i < N;i++){ st[H+i] = a[i]; pos[H+i] = i; } Arrays.fill(st, H+N, M, Integer.MAX_VALUE); for(int i = H-1;i >= 1;i--)propagate(i); } public void update(int pos, int x) { st[H+pos] = x; for(int i = (H+pos)>>>1;i >= 1;i >>>= 1)propagate(i); } private void propagate(int i) { if(st[2*i] <= st[2*i+1]){ st[i] = st[2*i]; pos[i] = pos[2*i]; }else{ st[i] = st[2*i+1]; pos[i] = pos[2*i+1]; } } public int minpos; public int minval; public int minx(int l, int r){ minval = Integer.MAX_VALUE; minpos = -1; if(l >= r)return minval; while(l != 0){ int f = l&-l; if(l+f > r)break; int v = st[(H+l)/f]; if(v < minval || v == minval && pos[(H+l)/f] < minpos){ minval = v; minpos = pos[(H+l)/f]; } l += f; } while(l < r){ int f = r&-r; int v = st[(H+r)/f-1]; if(v < minval || v == minval && pos[(H+r)/f-1] < minpos){ minval = v; minpos = pos[(H+r)/f-1]; } r -= f; } return minval; } public int min(int l, int r){ minpos = -1; minval = Integer.MAX_VALUE; min(l, r, 0, H, 1); return minval; } private void min(int l, int r, int cl, int cr, int cur) { if(l <= cl && cr <= r){ if(st[cur] < minval){ minval = st[cur]; minpos = pos[cur]; } }else{ int mid = cl+cr>>>1; if(cl < r && l < mid)min(l, r, cl, mid, 2*cur); if(mid < r && l < cr)min(l, r, mid, cr, 2*cur+1); } } } void run() throws Exception { is = INPUT.isEmpty() ? System.in : new ByteArrayInputStream(INPUT.getBytes()); out = new PrintWriter(System.out); long s = System.currentTimeMillis(); solve(); out.flush(); if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // Thread t = new Thread(null, null, "~", Runtime.getRuntime().maxMemory()){ // @Override // public void run() { // long s = System.currentTimeMillis(); // solve(); // out.flush(); // if(!INPUT.isEmpty())tr(System.currentTimeMillis()-s+"ms"); // } // }; // t.start(); // t.join(); } public static void main(String[] args) throws Exception { new G().run(); } private byte[] inbuf = new byte[1024]; public int lenbuf = 0, ptrbuf = 0; private int readByte() { if(lenbuf == -1)throw new InputMismatchException(); if(ptrbuf >= lenbuf){ ptrbuf = 0; try { lenbuf = is.read(inbuf); } catch (IOException e) { throw new InputMismatchException(); } if(lenbuf <= 0)return -1; } return inbuf[ptrbuf++]; } private boolean isSpaceChar(int c) { return !(c >= 33 && c <= 126); } private int skip() { int b; while((b = readByte()) != -1 && isSpaceChar(b)); return b; } private double nd() { return Double.parseDouble(ns()); } private char nc() { return (char)skip(); } private String ns() { int b = skip(); StringBuilder sb = new StringBuilder(); while(!(isSpaceChar(b))){ // when nextLine, (isSpaceChar(b) && b != ' ') sb.appendCodePoint(b); b = readByte(); } return sb.toString(); } private char[] ns(int n) { char[] buf = new char[n]; int b = skip(), p = 0; while(p < n && !(isSpaceChar(b))){ buf[p++] = (char)b; b = readByte(); } return n == p ? buf : Arrays.copyOf(buf, p); } private int[] na(int n) { int[] a = new int[n]; for(int i = 0;i < n;i++)a[i] = ni(); return a; } private long[] nal(int n) { long[] a = new long[n]; for(int i = 0;i < n;i++)a[i] = nl(); return a; } private char[][] nm(int n, int m) { char[][] map = new char[n][]; for(int i = 0;i < n;i++)map[i] = ns(m); return map; } private int[][] nmi(int n, int m) { int[][] map = new int[n][]; for(int i = 0;i < n;i++)map[i] = na(m); return map; } private int ni() { return (int)nl(); } private long nl() { long num = 0; int b; boolean minus = false; while((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-')); if(b == '-'){ minus = true; b = readByte(); } while(true){ if(b >= '0' && b <= '9'){ num = num * 10 + (b - '0'); }else{ return minus ? -num : num; } b = readByte(); } } private static void tr(Object... o) { System.out.println(Arrays.deepToString(o)); } }