#include <bits/stdc++.h>
using namespace std;
char a[300005], b[300005], c[300005];
bool cmp(int ac, int bc) { return ac > bc; }
int main() {
  cin >> a >> b;
  int n = strlen(a);
  int aa = 0, bb = 0, d = 0;
  sort(a, a + n);
  sort(b, b + n, cmp);
  int nn = (n - 1) / 2;
  int an = nn, bn = nn, k = n - 1;
  if (n % 2) bn--;
  for (int i = 0; i < n; i++) {
    if (i % 2) {
      if (b[bb] <= a[aa])
        c[k--] = b[bn--];
      else
        c[d++] = b[bb++];
    } else {
      if (a[aa] >= b[bb])
        c[k--] = a[an--];
      else
        c[d++] = a[aa++];
    }
  }
  cout << c;
  return 0;
}
