#include <bits/stdc++.h>
using namespace std;
template <typename T>
inline void read(T &x) {
  char c;
  bool nega = 0;
  while ((!isdigit(c = getchar())) && (c != '-'))
    ;
  if (c == '-') {
    nega = 1;
    c = getchar();
  }
  x = c - 48;
  while (isdigit(c = getchar())) x = x * 10 + c - 48;
  if (nega) x = -x;
}
template <typename T>
inline void writep(T x) {
  if (x > 9) writep(x / 10);
  putchar(x % 10 + 48);
}
template <typename T>
inline void write(T x) {
  if (x < 0) {
    putchar('-');
    x = -x;
  }
  writep(x);
}
template <typename T>
inline void writeln(T x) {
  write(x);
  putchar('\n');
}
string s, t;
int cnta[256];
int cntb[256];
char lowa, higha;
char lowb, highb;
int main() {
  cin >> s >> t;
  sort(s.begin(), s.end());
  sort(t.begin(), t.end());
  reverse(t.begin(), t.end());
  int n = s.size();
  s = '0' + s;
  for (int i = (n + 1) / 2; i >= 1; i--) cnta[s[i]]++;
  t = '0' + t;
  for (int i = n / 2; i >= 1; i--) cntb[t[i]]++;
  for (int i = 'a'; i <= 'z'; i++) {
    if (cnta[i]) higha = i;
    if (cntb[i]) highb = i;
  }
  for (int i = 'z'; i >= 'a'; i--) {
    if (cnta[i]) lowa = i;
    if (cntb[i]) lowb = i;
  }
  s = t = "";
  for (int i = 1; i <= n; i++) {
    if (i % 2) {
      if (lowa >= highb) {
        t += higha;
        cnta[higha]--;
        while (higha >= 'a' && cnta[higha] == 0) higha--;
      } else {
        s += lowa;
        cnta[lowa]--;
        while (lowa <= 'z' && cnta[lowa] == 0) lowa++;
      }
    } else {
      if (lowa >= highb) {
        t += lowb;
        cntb[lowb]--;
        while (lowb <= 'z' && cntb[lowb] == 0) lowb++;
      } else {
        s += highb;
        cntb[highb]--;
        while (highb >= 'a' && cntb[highb] == 0) highb--;
      }
    }
  }
  reverse(t.begin(), t.end());
  cout << s << t;
}
