#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 50;
const int INF = 0x3f3f3f3f;
const long long int INFL = 0x3f3f3f3f3f3f3f3f;
const double pi = atan(1.0) * 4.0;
int main(void) {
  char c1[N], c2[N];
  char ans[N];
  gets(c1);
  gets(c2);
  int tam = strlen(c1);
  sort(c1, c1 + tam);
  sort(c2, c2 + tam);
  int it = 0, itt = tam - 1;
  int id1 = 0, idd1 = (tam - 1) / 2;
  int id2 = 1 + (tam - 1) / 2, idd2 = tam - 1;
  ans[tam] = 0;
  for (int i = 0; i < tam; i++) {
    if (i % 2 == 0) {
      if (c2[idd2] <= c1[id1])
        ans[itt--] = c1[idd1--];
      else
        ans[it++] = c1[id1++];
    } else {
      if (c1[id1] >= c2[idd2])
        ans[itt--] = c2[id2++];
      else
        ans[it++] = c2[idd2--];
    }
  }
  puts(ans);
  return 0;
}
