#include <bits/stdc++.h>
using namespace std;
const int N = 300005;
bool cmp(char x, char y) { return x > y; }
char a[N], b[N], c[2 * N];
int main() {
  scanf("%s%s", a + 1, b + 1);
  int la = strlen(a + 1);
  int lb = strlen(b + 1);
  sort(a + 1, a + 1 + la);
  sort(b + 1, b + 1 + lb, cmp);
  int n = la;
  la = (n + 1) / 2;
  lb = n / 2;
  int qian = 0, hou = n + 1, p = -1;
  int pa = 1, push_back = 1;
  for (int i = 1; i <= n; ++i) {
    if (a[pa] >= b[push_back]) {
      p = i;
      break;
    }
    if (i & 1)
      c[i] = a[pa++];
    else
      c[i] = b[push_back++];
  }
  if (p != -1) {
    int q = n;
    int ppa = la, ppb = lb;
    for (int i = p; i <= n; ++i) {
      if (i & 1)
        c[q--] = a[ppa--];
      else
        c[q--] = b[ppb--];
    }
  }
  for (int i = 1; i <= n; ++i) printf("%c", c[i]);
  puts("");
  return 0;
}
