#include <bits/stdc++.h>
using namespace std;
template <class T>
inline void read(T& x) {
  bool f = false;
  char ch = getchar();
  x = 0;
  while (ch < 48) f = (ch == '-'), ch = getchar();
  while (ch >= 48) x = (x << 3) + (x << 1) + ch - 48, ch = getchar();
  if (f) x *= -1;
}
char a[333333], b[333333];
int aa[333333], bb[333333], n, cc[333333];
bool cmp(int a, int b) { return a > b; }
int main() {
  scanf("%s%s", a, b);
  n = strlen(a);
  for (int i = 1; i <= n; i++) aa[i] = a[i - 1];
  for (int i = 1; i <= n; i++) bb[i] = b[i - 1];
  sort(aa + 1, aa + n + 1);
  sort(bb + 1, bb + n + 1, cmp);
  int l = 1, r = n, al = 1, ar = n / 2 + n % 2, bl = 1, br = n / 2;
  for (int i = 1; i <= n / 2; i++) {
    if (aa[al] >= bb[bl])
      cc[r--] = aa[ar--];
    else
      cc[l++] = aa[al++];
    if (aa[al] >= bb[bl])
      cc[r--] = bb[br--];
    else
      cc[l++] = bb[bl++];
  }
  for (int i = 1; i <= n; i++)
    if (!cc[i]) cc[i] = aa[al];
  for (int i = 1; i <= n; i++) printf("%c", char(cc[i]));
}
