#include <bits/stdc++.h>
using namespace std;
const long long inf = 2147383647;
const double pi = 2 * acos(0.0);
const double eps = 1e-9;
struct debugger {
  template <typename T>
  debugger& operator,(const T& v) {
    cerr << v << " ";
    return *this;
  }
} dbg;
inline long long gcd(long long a, long long b) {
  a = ((a) < 0 ? -(a) : (a));
  b = ((b) < 0 ? -(b) : (b));
  while (b) {
    a = a % b;
    swap(a, b);
  }
  return a;
}
long long ext_gcd(long long A, long long B, long long* X, long long* Y) {
  long long x2, y2, x1, y1, x, y, r2, r1, q, r;
  x2 = 1;
  y2 = 0;
  x1 = 0;
  y1 = 1;
  for (r2 = A, r1 = B; r1 != 0;
       r2 = r1, r1 = r, x2 = x1, y2 = y1, x1 = x, y1 = y) {
    q = r2 / r1;
    r = r2 % r1;
    x = x2 - (q * x1);
    y = y2 - (q * y1);
  }
  *X = x2;
  *Y = y2;
  return r2;
}
inline long long modInv(long long a, long long m) {
  long long x, y;
  ext_gcd(a, m, &x, &y);
  if (x < 0) x += m;
  return x;
}
inline long long power(long long a, long long p) {
  long long res = 1, x = a;
  while (p) {
    if (p & 1) res = (res * x);
    x = (x * x);
    p >>= 1;
  }
  return res;
}
inline long long bigmod(long long a, long long p, long long m) {
  long long res = 1 % m, x = a % m;
  while (p) {
    if (p & 1) res = (res * x) % m;
    x = (x * x) % m;
    p >>= 1;
  }
  return res;
}
using namespace std;
template <typename T>
ostream& operator<<(ostream& out, vector<T> v) {
  out << "[ ";
  for (int i = 0; i < (((int)(v).size())); i++) {
    if (i) out << ", ";
    out << v[i];
  }
  out << " ]";
  return out;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& out, pair<T1, T2> p) {
  out << "( " << p.first << ", " << p.second << ")";
  return out;
}
template <typename T>
ostream& operator,(ostream& out, T x) {
  out << x << " ";
  return out;
}
char A[300007], B[300007];
int len;
int ast, aed, bst, bed;
char result[300007];
int st, ed;
int main() {
  scanf("%s", A);
  scanf("%s", B);
  len = strlen(A);
  sort(A, A + len);
  sort(B, B + len);
  ast = 0;
  aed = len / 2;
  aed--;
  if (len % 2) {
    aed++;
  }
  bst = aed + 1;
  bed = len - 1;
  st = 0;
  ed = len - 1;
  int who = 0;
  while (st <= ed) {
    if (who == 0) {
      if (B[bed] <= A[ast]) {
        result[ed] = A[aed];
        ed--;
        aed--;
      } else {
        result[st] = A[ast];
        ast++;
        st++;
      }
    } else {
      if (B[bed] <= A[ast]) {
        result[ed] = B[bst];
        bst++;
        ed--;
      } else {
        result[st] = B[bed];
        st++;
        bed--;
      }
    }
    who = 1 - who;
  }
  for (int i = 0; i < (len); i++) {
    printf("%c", result[i]);
  }
  printf("\n");
  return 0;
}
