#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>

#define FOR(i, x, n) for(int i = x; i < n; i++)
#define F0R(i, n) FOR(i, 0, n)
#define ROF(i, x, n) for(int i = n - 1; i >= x; i--)
#define R0F(i, n) ROF(i, 0, n)

#define WTF cout << "WTF" << endl

#define IOS ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define F first
#define S second
#define PB push_back
#define EP emplace_back

#define ALL(x) x.begin(), x.end()
#define RALL(x) x.rbegin(), x.rend()

using namespace std;

typedef long long LL;
typedef long double LD;

typedef pair<int, int> PII;
typedef pair<LL, LL> PLL;

typedef vector<int> VI;
typedef vector<LL> VLL;
typedef vector<PII> VPII;
typedef vector<PLL> VPLL;

typedef complex<LD> Point;

const int N = 2e5 + 7;
const int INF = 1e9 + 7;
const int LOG = 22;
const int A = 26;
const int SQ = 320;
const int MOD = 1e9 + 7;

int n;
int ns[N];

int main() {
    IOS;
    

    cin >> n;
    F0R(i, n) cin >> ns[i];

    int ans = -1;
    F0R(i, n) {
        FOR(j, 1, n) {
            if (i - j < 0 || i + j >= n) break;
            if (ns[i - j] != ns[i + j]) break;
            if (ns[i - j] >= ns[i - j + 1]) break;
            ans = max(ans, j * 2 + 1);
        }
    }

    cout <<ans;
}