#include <bits/stdc++.h>
const long long int mo = 1e9 + 7;
const long long int INF = 1e18;
const long double pi = acos(-1);
const int mxn = 5e5 + 5;
const int cons = 1;
using namespace std;
vector<char> oleg, igor;
char arr[mxn];
int oi, oj, ii, ij, ai, aj;
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  string a, b;
  int i, n;
  cin >> a >> b;
  n = a.length();
  for (i = 0; i < n; i++) {
    oleg.push_back(a[i]);
  }
  for (i = 0; i < n; i++) {
    igor.push_back(b[i]);
  }
  sort(oleg.begin(), oleg.end());
  sort(igor.begin(), igor.end());
  oi = 0, oj = (n + 1) / 2 - 1, ii = (n + 1) / 2, ij = n - 1, ai = 0,
  aj = n - 1;
  for (i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (oleg[oi] < igor[ij]) {
        arr[ai] = oleg[oi];
        oi++;
        ai++;
      } else {
        arr[aj] = oleg[oj];
        oj--;
        aj--;
      }
    } else {
      if (igor[ij] > oleg[oi]) {
        arr[ai] = igor[ij];
        ai++;
        ij--;
      } else {
        arr[aj] = igor[ii];
        aj--;
        ii++;
      }
    }
  }
  for (i = 0; i < n; i++) {
    cout << arr[i];
  }
  return 0;
}
