import java.io.*; import java.math.*; import java.util.*; import static java.util.Arrays.*; public class Main { private static final int mod = (int)1e9+7; final Random random = new Random(0); final IOFast io = new IOFast(); /// MAIN CODE public void run() throws IOException { // int TEST_CASE = Integer.parseInt(new String(io.nextLine()).trim()); int TEST_CASE = 1; while(TEST_CASE-- != 0) { int n = io.nextInt(); int[] A = io.nextIntArray(n); int[][] beam = new int[250][3]; // ans/prev/prev2 int[][] beam2 = new int[2*beam.length][3]; // ans/prev/prev2 int len = 0; beam[len][0] = 1; beam[len][1] = A[0]; beam[len++][2] = 0; beam[len][0] = 1; beam[len][1] = A[0]; beam[len++][2] = Integer.MAX_VALUE; HashTableLong h = new HashTableLong(); for(int i = 1; i < n; i++) { int len2 = 0; h.clear(); for(int j = 0; j < len; j++) { if(beam[j][2] != A[i] && beam[j][1] != A[i]) { if(beam[j][1] > beam[j][2] && beam[j][1] > A[i]) { if(h.get((long)A[i]<<32|beam[j][1]) < beam[j][0] + 1) { beam2[len2][0] = beam[j][0] + 1; beam2[len2][1] = A[i]; beam2[len2++][2] = beam[j][1]; h.put((long)A[i]<<32|beam[j][1], beam2[len2][0]); } } if(beam[j][1] < beam[j][2] && beam[j][1] < A[i]) { if(h.get((long)A[i]<<32|beam[j][1]) < beam[j][0] + 1) { beam2[len2][0] = beam[j][0] + 1; beam2[len2][1] = A[i]; beam2[len2++][2] = beam[j][1]; h.put((long)A[i]<<32|beam[j][1], beam2[len2][0]); } } } if(h.get((long)beam[j][1]<<32|beam[j][2]) < beam[j][0]) { beam2[len2][0] = beam[j][0]; beam2[len2][1] = beam[j][1]; beam2[len2++][2] = beam[j][2]; } } Arrays.sort(beam2, 0, len2, (a,b)->b[0]-a[0]); len = 0; for(int j = 0; j < beam.length; j++) { beam[len][0] = beam2[j][0]; beam[len][1] = beam2[j][1]; beam[len++][2] = beam2[j][2]; } } io.out.println(beam[0][0] < 3 ? 0 : beam[0][0]); } } static class HashTableLong { int gid; int[] id = new int[1<<22]; int[] table = new int[1<<22]; void clear() { gid++; } long get(long x) { int idx = (int)((x >>> 32 ^ (x)) & ((1<<22)-1)); return id[idx]==gid?table[idx]:0; } void put(long x, int v) { int idx = (int)((x >>> 32 ^ (x)) & ((1<<22)-1)); id[idx] = gid; table[idx] = v; } } /// TEMPLATE static int gcd(int n, int r) { return r == 0 ? n : gcd(r, n%r); } static long gcd(long n, long r) { return r == 0 ? n : gcd(r, n%r); } static void swap(T[] x, int i, int j) { T t = x[i]; x[i] = x[j]; x[j] = t; } static void swap(int[] x, int i, int j) { int t = x[i]; x[i] = x[j]; x[j] = t; } void main() throws IOException { // IOFast.setFileIO("rle-size.in", "rle-size.out"); try { run(); } catch (EndOfFileRuntimeException e) { } io.out.flush(); } public static void main(String[] args) throws IOException { new Main().main(); } static class EndOfFileRuntimeException extends RuntimeException { private static final long serialVersionUID = -8565341110209207657L; } static public class IOFast { private BufferedReader in = new BufferedReader(new InputStreamReader(System.in)); private PrintWriter out = new PrintWriter(System.out); void setFileIn(String ins) throws IOException { in.close(); in = new BufferedReader(new FileReader(ins)); } void setFileOut(String outs) throws IOException { out.flush(); out.close(); out = new PrintWriter(new FileWriter(outs)); } void setFileIO(String ins, String outs) throws IOException { setFileIn(ins); setFileOut(outs); } private static int pos, readLen; private static final char[] buffer = new char[1024 * 8]; private static char[] str = new char[500*8*2]; private static boolean[] isDigit = new boolean[256]; private static boolean[] isSpace = new boolean[256]; private static boolean[] isLineSep = new boolean[256]; static { for(int i = 0; i < 10; i++) { isDigit['0' + i] = true; } isDigit['-'] = true; isSpace[' '] = isSpace['\r'] = isSpace['\n'] = isSpace['\t'] = true; isLineSep['\r'] = isLineSep['\n'] = true; } public int read() throws IOException { if(pos >= readLen) { pos = 0; readLen = in.read(buffer); if(readLen <= 0) { throw new EndOfFileRuntimeException(); } } return buffer[pos++]; } public int nextInt() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; int ret = 0; if(str[0] == '-') { i = 1; } for(; i < len; i++) ret = ret * 10 + str[i] - '0'; if(str[0] == '-') { ret = -ret; } return ret; } public long nextLong() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); int i = 0; long ret = 0; if(str[0] == '-') { i = 1; } for(; i < len; i++) ret = ret * 10 + str[i] - '0'; if(str[0] == '-') { ret = -ret; } return ret; } public char nextChar() throws IOException { while(true) { final int c = read(); if(!isSpace[c]) { return (char)c; } } } int reads(int len, boolean[] accept) throws IOException { try { while(true) { final int c = read(); if(accept[c]) { break; } if(str.length == len) { char[] rep = new char[str.length * 3 / 2]; System.arraycopy(str, 0, rep, 0, str.length); str = rep; } str[len++] = (char)c; } } catch(EndOfFileRuntimeException e) { ; } return len; } int reads(char[] cs, int len, boolean[] accept) throws IOException { try { while(true) { final int c = read(); if(accept[c]) { break; } cs[len++] = (char)c; } } catch(EndOfFileRuntimeException e) { ; } return len; } public char[] nextLine() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isLineSep); try { if(str[len-1] == '\r') { len--; read(); } } catch(EndOfFileRuntimeException e) { ; } return Arrays.copyOf(str, len); } public String nextString() throws IOException { return new String(next()); } public char[] next() throws IOException { int len = 0; str[len++] = nextChar(); len = reads(len, isSpace); return Arrays.copyOf(str, len); } public int next(char[] cs) throws IOException { int len = 0; cs[len++] = nextChar(); len = reads(cs, len, isSpace); return len; } public double nextDouble() throws IOException { return Double.parseDouble(nextString()); } public long[] nextLongArray(final int n) throws IOException { final long[] res = new long[n]; for(int i = 0; i < n; i++) { res[i] = nextLong(); } return res; } public int[] nextIntArray(final int n) throws IOException { final int[] res = new int[n]; for(int i = 0; i < n; i++) { res[i] = nextInt(); } return res; } public int[][] nextIntArray2D(final int n, final int k) throws IOException { final int[][] res = new int[n][]; for(int i = 0; i < n; i++) { res[i] = nextIntArray(k); } return res; } public int[][] nextIntArray2DWithIndex(final int n, final int k) throws IOException { final int[][] res = new int[n][k+1]; for(int i = 0; i < n; i++) { for(int j = 0; j < k; j++) { res[i][j] = nextInt(); } res[i][k] = i; } return res; } public double[] nextDoubleArray(final int n) throws IOException { final double[] res = new double[n]; for(int i = 0; i < n; i++) { res[i] = nextDouble(); } return res; } } }