10534

#include <algorithm>
#include <bitset>
#include <cctype>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <iostream>
#include <list>
#include <climits>
#include <map>
#include <memory>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#include <iomanip>

using namespace std;

#define REP(i,n) for(__typeof(n) i=0; i<(n); i++)
#define FOR(i,a,b) for(__typeof(b) i=(a); i<=(b); i++)
#define RESET(t,value) memset((t), value, sizeof(t))

#define READ(f) freopen(f, "r", stdin)

#define INF (1<<30)
#define pb push_back

#define Range 10010

int dp[Range], L[Range];
int x[Range];
int I[Range];
int pos, N;
vector <int> listSequence, ldSequence;
void LisNlogk() {
    int i;
    memset(I, INF, sizeof I);
    I[0] = -INF;

    int trackPosition = 0;
    int max = -INF;
    for(i = 0; i <= N; i++ ) {
        int begin, end, mid;
        begin = 0;
        end = trackPosition;
        while( begin <= end ) {
            mid = ( begin + end ) / 2;
            if( I[mid] < x[i] )
                begin = mid + 1;
            else
                end = mid - 1;
        }
        I[begin] = x[i];
        dp[i] = begin;
        if(dp[i] > max) {
            max = dp[i];
            pos = i;
        }
        if( trackPosition < begin )
            trackPosition = begin;
    }
}

void sequence() {
    listSequence.clear();
    listSequence.pb(x[pos]);
    for(int i = pos-1; i >= 0; i--) {
        if( x[i] < x[pos] &&  dp[i] == dp[pos] -1) {
            pos = i;
            listSequence.pb(x[i]);
        }
    }
}

void LdsNlogk() {
    int i;
    memset(I, -INF, sizeof I);
    I[0] = INF;

    int trackPosition = 0;
    int Max = -INF;
    for(i = 0; i <= N; i++ ) {
        int begin, end, mid;
        begin = 0;
        end = trackPosition;
        while( begin <= end ) {
            mid = ( begin + end ) / 2;
            if( I[mid] > x[i] )
                begin = mid + 1;
            else
                end = mid - 1;
        }
        I[begin] = x[i];
        dp[i] = begin;
        if(dp[i] > Max) {
            Max = dp[i];
            pos = i;
        }
        if( trackPosition < begin )
            trackPosition = begin;
    }
}

void decreasingSeq() {
    ldSequence.clear();
    ldSequence.pb(x[pos]);
    for(int i = pos-1; i >= 0; i--) {
        if( x[i] > x[pos] &&  dp[i] == dp[pos] - 1) {
            pos = i;
            ldSequence.pb(x[i]);
        }
    }
}

int main() {
    //READ("inputs.txt");
    int n;
    while (cin >> n) {
        REP(i, n) cin >> x[i];
        N = n - 1;
        LdsNlogk();
        decreasingSeq();
        LisNlogk();
        sequence();
        int result = -1;
        reverse(listSequence.begin(), listSequence.end());
        for(int i = listSequence.size() - 1; i >= 0; i--) {
            REP( j, ldSequence.size() ) {
                if(listSequence[i] == ldSequence[j]) {
                    result = (i+1) * 2 - 1;
                    break;
                }
            }
            if(result != -1) break;
        }
        cout << result << "\n";
    }

    return EXIT_SUCCESS;
}