package gioku2020day1; 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(); int[] a = na(n); a = shrink(a); int ans = go(a); for(int i = 0;i < n;i++)a[i] = n - 1 - a[i]; ans = Math.max(ans, go(a)); out.println(ans); } int go(int[] a) { int n = a.length; int[] pre = new int[n]; SegmentTreeRMQ st = new SegmentTreeRMQ(n+1); for(int i = 0;i < n;i++){ pre[i] = Math.max(0, -st.minx(0, a[i])); st.update(a[i], -(pre[i] + 1)); } st = new SegmentTreeRMQ(n+1); int[] suf = new int[n]; for(int i = n-1;i >= 0;i--){ suf[i] = Math.max(0, -st.minx(0, a[i])); st.update(a[i], -(suf[i] + 1)); } int ans = 0; for(int i = 0;i < n;i++){ ans = Math.max(ans, Math.min(pre[i], suf[i])); } return ans; } public static class SegmentTreeRMQ { public int M, H, N; public int[] st; public SegmentTreeRMQ(int n) { N = n; M = Integer.highestOneBit(Math.max(N-1, 1))<<2; H = M>>>1; st = new int[M]; Arrays.fill(st, 0, M, Integer.MAX_VALUE); } public SegmentTreeRMQ(int[] a) { N = a.length; M = Integer.highestOneBit(Math.max(N-1, 1))<<2; H = M>>>1; st = new int[M]; for(int i = 0;i < N;i++){ st[H+i] = a[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) { st[i] = Math.min(st[2*i], st[2*i+1]); } public int minx(int l, int r){ int min = Integer.MAX_VALUE; if(l >= r)return min; while(l != 0){ int f = l&-l; if(l+f > r)break; int v = st[(H+l)/f]; if(v < min)min = v; l += f; } while(l < r){ int f = r&-r; int v = st[(H+r)/f-1]; if(v < min)min = v; r -= f; } return min; } public int min(int l, int r){ return l >= r ? 0 : min(l, r, 0, H, 1);} private int min(int l, int r, int cl, int cr, int cur) { if(l <= cl && cr <= r){ return st[cur]; }else{ int mid = cl+cr>>>1; int ret = Integer.MAX_VALUE; if(cl < r && l < mid){ ret = Math.min(ret, min(l, r, cl, mid, 2*cur)); } if(mid < r && l < cr){ ret = Math.min(ret, min(l, r, mid, cr, 2*cur+1)); } return ret; } } public int firstle(int l, int v) { if(l >= H)return -1; int cur = H+l; while(true){ if(st[cur] <= v){ if(cur >= H)return cur-H; cur = 2*cur; }else{ cur++; if((cur&cur-1) == 0)return -1; if((cur&1)==0)cur>>>=1; } } } public int lastle(int l, int v) { if(l < 0)return -1; int cur = H+l; while(true){ if(st[cur] <= v){ if(cur >= H)return cur-H; cur = 2*cur + 1; }else{ if((cur&cur-1) == 0)return -1; cur--; if((cur&1)==1)cur>>>=1; } } } } public static int[] shrink(int[] a) { int n = a.length; long[] b = new long[n]; for (int i = 0; i < n; i++) b[i] = (long) a[i] << 32 | i; Arrays.sort(b); int[] ret = new int[n]; int p = 0; for (int i = 0; i < n; i++) { if (i > 0 && (b[i] ^ b[i - 1]) >> 32 != 0) p++; ret[(int) b[i]] = p; } return ret; } 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)); } }