#include <bits/stdc++.h>
using namespace std;
const long double PI = acosl(-1.0);
const double EPS = 1e-12;
void showBit(int no, int N) {
  for (int i = N - 1; i >= 0; i--)
    if ((no >> i) & 1)
      printf("1");
    else
      printf("0");
  printf("\n");
}
int binToDec(string s) {
  int ln = s.length();
  int sum = 0;
  for (int i = ln - 1, k = 0; i >= 0; i--, k++)
    sum = sum + (s[i] - '0') * (1 << k);
  return sum;
}
void combination(long long com[][1005]) {
  com[0][0] = 1;
  int sz = 1000;
  for (int i = 1; i <= sz; i++) {
    com[i][0] = 1;
    for (int j = 1; j <= i; j++) {
      com[i][j] = com[i - 1][j] + com[i - 1][j - 1];
      com[i][j] = com[i][j] % 1000000007;
    }
  }
}
int find_par(int cn) {}
int gcd(int u, int v) {
  if (v == 0) return u;
  return gcd(v, u % v);
}
void insert_ind(int cs, int ci, int s, int e) {
  if (s == e) {
    return;
  }
  int mid = (s + e) / 2;
  if (ci <= mid)
    insert_ind(2 * cs, ci, s, mid);
  else
    insert_ind(2 * cs + 1, ci, mid + 1, e);
}
void update_ind(int cs, int ci, int s, int e, int val) {
  if (s == e) {
    return;
  }
  int mid = (s + e) / 2;
  if (ci <= mid)
    update_ind(2 * cs, ci, s, mid, val);
  else
    update_ind(2 * cs + 1, ci, mid + 1, e, val);
}
void update_seg(int cs, int ds, int de, int s, int e, int val) {
  if (ds == s && de == e) {
    return;
  }
  int mid = (s + e) / 2;
  if (ds <= mid) update_seg(2 * cs, ds, min(mid, de), s, mid, val);
  if (de > mid) update_seg(2 * cs + 1, max(mid + 1, ds), de, mid + 1, e, val);
}
void pattern_match(char pat[], const int len, int pi[]) {
  pi[1] = 0;
  for (int i = 2; i <= len; i++) {
    int st = i - 1;
    while (st >= 0 && pat[pi[st] + 1] != pat[i]) st = pi[st];
    if (st == 0)
      pi[i] = 0;
    else
      pi[i] = pi[st] + 1;
  }
}
void pattern_match(char pat[], int pi[], char tar[], const int len1, int gi[]) {
  if (pat[0] == tar[0]) gi[0] = 1;
  for (int i = 1; i < len1; i++) {
    int st = gi[i - 1];
    while (pat[st] != tar[i]) {
      if (st == 0) {
        st = -1;
        break;
      }
      st = pi[st - 1];
    }
    if (st == -1)
      gi[i] = 0;
    else
      gi[i] = st + 1;
  }
}
struct myArray {
  int mat[10][10];
};
myArray matrix_mul(myArray mat1, myArray mat2, const int sz) {
  int tmp[sz][sz];
  memset((tmp), 0, sizeof((tmp)));
  for (int r = 0; r < sz; r++)
    for (int c = 0; c < sz; c++)
      for (int cr = 0; cr < sz; cr++)
        tmp[r][c] += mat1.mat[r][cr] * mat2.mat[c][cr];
  myArray res;
  for (int r = 0; r < sz; r++)
    for (int c = 0; c < sz; c++) res.mat[r][c] = tmp[r][c];
  return res;
}
myArray unit_matrix(const int sz) {
  myArray ma;
  memset((ma.mat), 0, sizeof((ma.mat)));
  for (int i = 0; i < sz; i++) ma.mat[i][i] = 1;
  return ma;
}
myArray matrix_expo(int p, myArray mat, const int sz) {
  if (p == 0) {
    return unit_matrix(sz);
  }
  if (p & 1) return matrix_mul(mat, matrix_expo(p - 1, mat, sz), sz);
  myArray tmp = matrix_expo(p >> 1, mat, sz);
  return matrix_mul(tmp, tmp, sz);
}
int X[] = {0, 0, 1, -1};
int Y[] = {1, -1, 0, 0};
int k, x, n, m;
char s1[105], s2[105];
void makeString(int rp, int fl, int fr, char s[], int ln) {
  bool print = false;
  s[0] = '\0';
  int r = ln - (rp * 2);
  if (rp == 0) {
    if (ln == 2 && fl == 0 && fr == 2) return;
    if (ln == 1 && fl != fr) return;
    s[0] = 'A' + fl;
    for (int i = 1; i < ln - 1; i++) s[i] = 'B';
    s[ln - 1] = 'A' + fr;
    s[ln] = '\0';
  } else {
    if (r == 0) {
      if (!(fl == 0 && fr == 2)) return;
      for (int i = 0; i < ln; i++) s[i] = (i & 1) ? 'C' : 'A';
      s[ln] = '\0';
    } else if (r == 1) {
      if (fl == 0) {
        for (int i = 0; i < ln - 1; i++) s[i] = (i & 1) ? 'C' : 'A';
        s[ln - 1] = 'A' + fr;
        s[ln] = '\0';
      } else if (fr == 2) {
        s[0] = 'A' + fl;
        for (int i = 1; i < ln; i++) s[i] = (i & 1) ? 'A' : 'C';
        s[ln] = '\0';
      }
    } else {
      s[0] = 'A' + fl;
      for (int i = 1; i <= rp; i++) {
        s[2 * i - 1] = 'A';
        s[2 * i] = 'C';
      }
      for (int i = 1 + 2 * rp; i < ln; i++) s[i] = 'A' + fr;
      s[ln] = '\0';
    }
  }
}
int cal(int rp1, int fl, int fr, int rp2, int sl, int sr) {
  int crp = 0, t = 0;
  bool print = false;
  for (int i = 3; i <= k; i++) {
    crp = rp1 + rp2;
    if (fr == 0 && sl == 2) crp++;
    t = crp;
    if (t > x) return -1;
    int tfl = fl;
    rp1 = rp2;
    fl = sl;
    fr = sr;
    rp2 = crp;
    sl = tfl;
    sr = sr;
  }
  return t;
}
int main() {
  cin >> k >> x >> n >> m;
  for (int i = 0; i <= n / 2; i++)
    for (int j = 0; j <= m / 2; j++)
      for (int fl = 0; fl < 3; fl++)
        for (int fr = 0; fr < 3; fr++)
          for (int sl = 0; sl < 3; sl++)
            for (int sr = 0; sr < 3; sr++) {
              makeString(i, fl, fr, s1, n);
              makeString(j, sl, sr, s2, m);
              if (s1[0] == '\0' || s2[0] == '\0') continue;
              int res = cal(i, fl, fr, j, sl, sr);
              if (res == x) {
                puts(s1);
                puts(s2);
                return 0;
              }
            }
  printf("Happy new year!");
  return 0;
}
