#include <bits/stdc++.h>
using namespace std;
int main() {
  string s, t;
  cin >> s >> t;
  vector<char> oleg, igor;
  int n = s.size();
  for (int i = 0; i < n; i++) {
    oleg.push_back(s[i]);
    igor.push_back(t[i]);
  }
  sort(oleg.begin(), oleg.end());
  sort(igor.begin(), igor.end());
  reverse(igor.begin(), igor.end());
  string ans;
  for (int i = 0; i < n; i++) ans += '?';
  int lInd = 0, rInd = n - 1;
  int igorIndex[2], olegIndex[2];
  igorIndex[0] = olegIndex[0] = 0;
  igorIndex[1] = n / 2 - 1;
  olegIndex[1] = (n + 1) / 2 - 1;
  for (int i = 0; i < n; i++) {
    if (i % 2) {
      if (igor[igorIndex[0]] <= oleg[olegIndex[0]]) {
        ans[rInd] = igor[igorIndex[1]];
        rInd--;
        igorIndex[1]--;
      } else {
        ans[lInd] = igor[igorIndex[0]];
        lInd++;
        igorIndex[0]++;
      }
    } else {
      if (oleg[olegIndex[0]] >= igor[igorIndex[0]]) {
        ans[rInd] = oleg[olegIndex[1]];
        rInd--;
        olegIndex[1]--;
      } else {
        ans[lInd] = oleg[olegIndex[0]];
        lInd++;
        olegIndex[0]++;
      }
    }
  }
  cout << ans << endl;
}
