#include <bits/stdc++.h>
using namespace std;
char a[300000 + 5], b[300000 + 5], c[300000 + 5];
bool cmp(char x, char y) { return x > y; }
int main() {
  int n, i, al, ar, bl, br, cl, cr;
  scanf("%s%s", a, b);
  n = strlen(a);
  sort(a, a + n);
  sort(b, b + n, cmp);
  al = 0;
  ar = n + 1 >> 1;
  bl = 0;
  br = n >> 1;
  cl = 0;
  cr = n;
  for (i = 0; i < n; ++i)
    if (i & 1)
      if (b[bl] > a[al])
        c[cl++] = b[bl++];
      else
        c[--cr] = b[--br];
    else if (a[al] < b[bl])
      c[cl++] = a[al++];
    else
      c[--cr] = a[--ar];
  puts(c);
}
