//#define NDEBUG
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <iterator>
#include <vector>

namespace n91 {

using i8 = std::int_fast8_t;
using i32 = std::int_fast32_t;
using i64 = std::int_fast64_t;
using u8 = std::uint_fast8_t;
using u32 = std::uint_fast32_t;
using u64 = std::uint_fast64_t;
using isize = std::ptrdiff_t;
using usize = std::size_t;

constexpr usize operator"" _z(unsigned long long x) noexcept {
  return static_cast<usize>(x);
}

template <class T> class integral_iterator {
public:
  using difference_type = T;
  using value_type = T;
  using pointer = const value_type *;
  using reference = value_type;
  using iterator_category = std::random_access_iterator_tag;

private:
  using self_type = integral_iterator<value_type>;
  value_type i;

public:
  constexpr integral_iterator() noexcept : i() {}
  explicit constexpr integral_iterator(const value_type i) noexcept : i(i) {}
  constexpr self_type operator++(int) noexcept { return self_type(i++); }
  constexpr self_type operator--(int) noexcept { return self_type(i--); }
  constexpr self_type operator[](const difference_type rhs) const noexcept {
    return self_type(i + rhs);
  }
  constexpr self_type &operator++() noexcept {
    ++i;
    return *this;
  }
  constexpr self_type &operator--() noexcept {
    --i;
    return *this;
  }
  constexpr reference operator*() const noexcept { return i; }
  constexpr self_type operator+(const difference_type rhs) const noexcept {
    return self_type(i + rhs);
  }
  constexpr self_type operator-(const difference_type rhs) const noexcept {
    return self_type(i - rhs);
  }
  constexpr difference_type operator-(const self_type rhs) const noexcept {
    return i - rhs.i;
  }
  constexpr bool operator<(const self_type rhs) const noexcept {
    return i < rhs.i;
  }
  constexpr bool operator<=(const self_type rhs) const noexcept {
    return i <= rhs.i;
  }
  constexpr bool operator>(const self_type rhs) const noexcept {
    return i > rhs.i;
  }
  constexpr bool operator>=(const self_type rhs) const noexcept {
    return i >= rhs.i;
  }
  constexpr bool operator==(const self_type rhs) const noexcept {
    return i == rhs.i;
  }
  constexpr bool operator!=(const self_type rhs) const noexcept {
    return i != rhs.i;
  }
  constexpr self_type &operator+=(const difference_type rhs) noexcept {
    i += rhs;
    return *this;
  }
  constexpr self_type &operator-=(const difference_type rhs) noexcept {
    i -= rhs;
    return *this;
  }
};
template <class T>
constexpr integral_iterator<T> make_int_itr(const T i) noexcept {
  return integral_iterator<T>(i);
}
class rep {
  const usize f, l;

public:
  constexpr rep(const usize f, const usize l) noexcept : f(f), l(l) {}
  constexpr auto begin() const noexcept { return make_int_itr(f); }
  constexpr auto end() const noexcept { return make_int_itr(l); }
};
class revrep {
  const usize f, l;

public:
  revrep(const usize f, const usize l) noexcept : f(l), l(f) {}
  auto begin() const noexcept {
    return std::make_reverse_iterator(make_int_itr(f));
  }
  auto end() const noexcept {
    return std::make_reverse_iterator(make_int_itr(l));
  }
};
template <class T> auto md_vec(const usize n, const T &value) {
  return std::vector<T>(n, value);
}
template <class... Args> auto md_vec(const usize n, Args... args) {
  return std::vector<decltype(md_vec(args...))>(n, md_vec(args...));
}
template <class T> constexpr T difference(const T &a, const T &b) {
  return a < b ? b - a : a - b;
}
template <class T> T scan() {
  T ret;
  std::cin >> ret;
  return ret;
}

} // namespace n91

#include <algorithm>
#include <cassert>
#include <iostream>
#include <string>
#include <utility>

namespace n91 {

void main_() {
  const usize n = scan<usize>();
  const std::string s = scan<std::string>();
  isize x = static_cast<isize>(0);
  isize y = static_cast<isize>(0);
  for (const auto e : s) {
    if ('A' <= e && e <= 'M') {
      --x;
    } else if ('N' <= e && e <= 'Z') {
      ++x;
    } else if ('a' <= e && e <= 'm') {
      ++y;
    } else if ('n' <= e && e <= 'z') {
      --y;
    } else {
      assert(false);
    }
  }
  const std::string ans =
      std::string(std::abs(x), x < static_cast<isize>(0) ? 'A' : 'N') +
      std::string(std::abs(y), y < static_cast<isize>(0) ? 'n' : 'a');
  std::cout << ans.size() << std::endl << ans << std::endl;
}

} // namespace n91

int main() {
  n91::main_();
  return 0;
}



Measured memory_bytes: 3340