#include <bits/stdc++.h>
using namespace std;
char a[300010], b[300010], c[300010];
int main() {
  scanf("%s %s", a, b);
  int n = strlen(a);
  sort(a, a + n);
  sort(b, b + n);
  int a1 = 0, a2 = (n - 1) / 2, b2 = (n - 1) / 2 + 1, b1 = n - 1, c1 = 0,
      c2 = n - 1;
  for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
      if (a[a1] >= b[b1]) {
        c[c2--] = a[a2--];
      } else {
        c[c1++] = a[a1++];
      }
    } else {
      if (a[a1] >= b[b1]) {
        c[c2--] = b[b2++];
      } else {
        c[c1++] = b[b1--];
      }
    }
  }
  printf("%s\n", c);
  return 0;
}
