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#include <bits/stdc++.h>

using namespace std;


signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int n;
    cin >> n;

    vector<int> a(n), pos(n + 1);
    for (int i = 0; i < n; i++) cin >> a[i], pos[a[i]] = i + 1;

    int cnt = 0;

    for (int i = 1; i <= n; i++) {
        while (i + 1 <= n && pos[i] < pos[i + 1]) i++;
        cnt++;
    }

    for (int i = 0; i < 64; i++) {
        if ((1LL << i) >= cnt) return cout << i << endl, 0;
    }

    assert(false);

}