#include <bits/stdc++.h>
using namespace std;
int l1[2], l2[2], i, j, k, n, m, S[300010], M[2], s = 1, t;
char c[2][300010];
bool b;
inline bool Cmp(char a, char b) { return a > b; }
int main() {
  scanf("%s%s", c[0], c[1]);
  n = strlen(c[0]);
  t = n;
  sort(c[0], c[0] + n);
  sort(c[1], c[1] + n, Cmp);
  l2[0] = (n + 1) / 2 - 1;
  l2[1] = n / 2 - 1;
  for (i = 1; i <= n; i++, b ^= 1) {
    if (c[0][l1[0]] < c[1][l1[1]])
      S[s++] = c[b][l1[b]++];
    else
      S[t--] = c[b][l2[b]--];
  }
  for (i = 1; i <= n; i++) putchar(S[i]);
  return 0;
}
