#include <bits/stdc++.h>
using namespace std;
char a[300010];
char b[300010];
char res[300010];
int cmp(int x, int y) { return x > y; }
int main() {
  int na, nb, cnt, pa, qa, pb, qb, l, r, L;
  while (scanf("%s%s", a, b) != EOF) {
    cnt = 0;
    na = strlen(a);
    L = na;
    nb = strlen(b);
    sort(a, a + na);
    sort(b, b + nb, cmp);
    if (na % 2 == 1)
      na = na / 2 + 1;
    else
      na = na / 2;
    nb = L - na;
    pa = 0;
    qa = na - 1;
    pb = 0;
    qb = nb - 1;
    l = 0;
    r = L - 1;
    for (int i = 0; i < L; i++) {
      if (i % 2 == 0) {
        if (a[pa] >= b[pb])
          res[r--] = a[qa--];
        else
          res[l++] = a[pa++];
      } else {
        if (a[pa] >= b[pb])
          res[r--] = b[qb--];
        else
          res[l++] = b[pb++];
      }
    }
    res[L] = '\0';
    printf("%s", res);
    printf("\n");
  }
  return 0;
}
