#include <algorithm>
#include <vector>

int flags(const std::vector<int>& a)
{
    int size = static_cast<int>(a.size());
    if (size == 0) {
        return 0;
    }

    std::vector<bool> peaks(size, false);
    for (int i = 1; i < size; ++i) {
        int nextVal = (i + 1 < size) ? a[i + 1] : 0;
        peaks[i] = a[i - 1] < a[i] && a[i] > nextVal;
    }

    std::vector<int> next(size);
    next[size - 1] = -1;
    for (int i = size - 2; i >= 0; --i) {
        next[i] = peaks[i] ? i : next[i + 1];
    }

    int i = 1;
    int result = 0;
    while (i * (i - 1) <= size) {
        int pos = 0;
        int num = 0;
        while (pos < size && num < i) {
            pos = next[pos];
            if (pos == -1) {
                break;
            }
            ++num;
            pos += i;
        }
        ++i;
        result = std::max(result, num);
    }

    return result;
}