#include <bits/stdc++.h>

using i32 = std::int32_t;
using u32 = std::uint32_t;
using i64 = std::int64_t;
using u64 = std::uint64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

class rep {
    struct Iter {
        usize itr;
        constexpr Iter(const usize pos) noexcept : itr(pos) {}
        constexpr void operator++() noexcept { ++itr; }
        constexpr bool operator!=(const Iter& other) const noexcept { return itr != other.itr; }
        constexpr usize operator*() const noexcept { return itr; }
    };
    const Iter first, last;

  public:
    explicit constexpr rep(const usize first, const usize last) noexcept : first(first), last(std::max(first, last)) {}
    constexpr Iter begin() const noexcept { return first; }
    constexpr Iter end() const noexcept { return last; }
};

template <class T> using Vec = std::vector<T>;

void main_() {
    usize N, K;
    std::cin >> N >> K;
    Vec<i32> A(N), B(N);
    for (auto& x : A) std::cin >> x;
    for (auto& x : B) std::cin >> x;
    Vec<std::pair<i64, usize>> pair(N);
    for (const auto i : rep(0, N)) {
        pair[i] = {A[i] - B[i], i};
    }
    std::sort(pair.rbegin(), pair.rend());
    std::string ans(N, 'B');
    for (const auto i : rep(0, K)) {
        ans[pair[i].second] = 'A';
    }
    std::cout << ans << '\n';
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(nullptr);
    main_();
    return 0;
}