#include <bits/stdc++.h>
using namespace std;
const double pi = acos(-1.0);
const int intmax = 0x3f3f3f3f;
const long long lldmax = 0x3f3f3f3f3f3f3f3fll;
double eps = 1e-8;
template <class T>
inline void checkmin(T &a, T b) {
  if (b < a) a = b;
}
template <class T>
inline void checkmax(T &a, T b) {
  if (b > a) a = b;
}
template <class T>
inline T sqr(T x) {
  return x * x;
}
template <class T>
inline T lowbit(T n) {
  return (n ^ (n - 1)) & n;
}
template <class T>
inline int countbit(T n) {
  return (n == 0) ? 0 : (1 + countbit(n & (n - 1)));
}
template <class T>
inline T checkmod(T n, T m) {
  return (n % m + m) % m;
}
inline int rand(int a, int b) {
  if (a >= b) return a;
  return rand() % (b - a) + a;
}
template <class T>
inline T lcm(T a, T b) {
  if (a < 0) return lcm(-a, b);
  if (b < 0) return lcm(a, -b);
  return a * (b / gcd(a, b));
}
template <class T>
inline T gcd(T a, T b) {
  if (a < 0) return gcd(-a, b);
  if (b < 0) return gcd(a, -b);
  return (b == 0) ? a : gcd(b, a % b);
}
template <class T>
inline T euclid(T a, T b, T &x, T &y) {
  if (a < 0) {
    T d = euclid(-a, b, x, y);
    x = -x;
    return d;
  }
  if (b < 0) {
    T d = euclid(a, -b, x, y);
    y = -y;
    return d;
  }
  if (b == 0) {
    x = 1;
    y = 0;
    return a;
  } else {
    T d = euclid(b, a % b, x, y);
    T t = x;
    x = y;
    y = t - (a / b) * y;
    return d;
  }
}
template <class T>
inline vector<pair<T, int> > factorize(T n) {
  vector<pair<T, int> > R;
  for (T i = 2; n > 1;) {
    if (n % i == 0) {
      int C = 0;
      for (; n % i == 0; C++, n /= i)
        ;
      R.push_back(make_pair(i, C));
    }
    i++;
    if (i > n / i) i = n;
  }
  if (n > 1) R.push_back(make_pair(n, 1));
  return R;
}
template <class T>
inline bool isPrimeNumber(T n) {
  if (n <= 1) return false;
  for (T i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
template <class T>
inline T eularFunction(T n) {
  vector<pair<T, int> > R = factorize(n);
  T r = n;
  for (int i = 0; i < R.size(); i++) r = r / R[i].first * (R[i].first - 1);
  return r;
}
template <class T>
inline int dblcmp(T a, const T b) {
  a -= b;
  return a > eps ? 1 : (a < -eps ? -1 : 0);
}
template <class T>
inline int sgn(T a) {
  return a > eps ? 1 : (a < -eps ? -1 : 0);
}
const int N = 110;
int k, x, n, m;
long long dp[N];
char ca[N], cb[N];
bool gao(int nn, int mm, int sa, int ta, int sb, int tb) {
  if (2 * nn + sa + ta > n) return false;
  if (2 * mm + sb + tb > m) return false;
  dp[1] = nn;
  dp[2] = mm;
  dp[3] = nn + mm + (ta & sb);
  for (int i = 4; i <= k; ++i) {
    dp[i] = dp[i - 1] + dp[i - 2];
    if (i % 2 == 0)
      dp[i] += tb & sa;
    else
      dp[i] += tb & sb;
    checkmin(dp[i], x + 1LL);
  }
  return dp[k] == x;
}
bool print(int nn, int mm, int sa, int ta, int sb, int tb) {
  memset(ca, 'B', sizeof(ca));
  memset(cb, 'B', sizeof(cb));
  ca[n] = 0, cb[m] = 0;
  int s = 0;
  if (sa) {
    ca[s++] = 'C';
  }
  for (int i = 0; i < nn; ++i) {
    ca[s++] = 'A';
    ca[s++] = 'C';
  }
  if (ta) ca[n - 1] = 'A';
  s = 0;
  if (sb) {
    cb[s++] = 'C';
  }
  for (int i = 0; i < mm; ++i) {
    cb[s++] = 'A';
    cb[s++] = 'C';
  }
  if (tb) cb[m - 1] = 'A';
  puts(ca);
  puts(cb);
}
int main() {
  cin >> k >> x >> n >> m;
  for (int i = 0; 2 * i <= n; ++i) {
    for (int j = 0; 2 * j <= m; ++j) {
      for (int k = 0; k <= 1; ++k)
        for (int l = 0; l <= 1; ++l)
          for (int kk = 0; kk <= 1; ++kk)
            for (int ll = 0; ll <= 1; ll++) {
              if (gao(i, j, k, l, kk, ll)) {
                print(i, j, k, l, kk, ll);
                return 0;
              }
            }
    }
  }
  puts("Happy new year!");
  return 0;
}
