#include <bits/stdc++.h>
using namespace std;
char olegs[300100];
char igors[300100];
char res[300100];
int a, b, h, w, n;
int main() {
  cin >> olegs;
  cin >> igors;
  int len = strlen(olegs);
  int n = len;
  sort(olegs, olegs + len);
  sort(igors, igors + len);
  int osi = 0, oei, igsi = 0, igei;
  igsi = n - (len / 2);
  igei = len - 1;
  oei = len / 2;
  if (len % 2 == 0) oei = oei - 1;
  int olegsturn = 1;
  int i;
  int rsi = 0, rei = n - 1;
  while (rsi <= rei) {
    if (olegsturn) {
      if (olegs[osi] >= igors[igei]) {
        res[rei--] = olegs[oei--];
      } else {
        res[rsi++] = olegs[osi++];
      }
    } else {
      if (igors[igei] <= olegs[osi]) {
        res[rei--] = igors[igsi++];
      } else {
        res[rsi++] = igors[igei--];
      }
    }
    olegsturn = !olegsturn;
  }
  for (i = 0; i < n; i++) cout << res[i];
  return 0;
}
