#include <bits/stdc++.h>
using namespace std;
bool chk(char a, char b) { return a > b; }
int main() {
  long long int n, x1 = 0, y1, x2 = 0, y2, p = 0, q, op = 0, pu, z;
  string s1, s2;
  cin >> s1 >> s2;
  char out[s2.size()];
  z = s2.size();
  q = z - 1;
  sort(s1.begin(), s1.end());
  sort(s2.begin(), s2.end(), chk);
  n = (s1.size() + 1) / 2;
  s1.erase(s1.begin() + n, s1.end());
  n = s2.size() / 2;
  s2.erase(s2.begin() + n, s2.end());
  y1 = s1.size() - 1, y2 = s2.size() - 1;
  for (int i = 0; i < z; i++) {
    if (i % 2) {
      if (s2[x2] <= s1[x1]) {
        out[q] = s2[y2];
        y2--;
        q--;
        op = q;
      } else {
        out[p] = s2[x2];
        x2++;
        p++;
        op = p;
      }
    } else {
      if (z % 2 && i == z - 1) {
        pu ? out[op] = s1[y1] : out[op] = s1[x1];
        break;
      }
      if (s1[x1] >= s2[x2]) {
        out[q] = s1[y1];
        q--;
        y1--;
        pu = 1;
      } else {
        out[p] = s1[x1];
        p++;
        x1++;
        pu = 0;
      }
    }
  }
  for (int i = 0; i < z; i++) cout << out[i];
}
