#include "bits/stdc++.h"
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
#define ll long long
#define ull unsigned long long
#define OPEN freopen (".in", "r", stdin); freopen (".out", "w", stdout);
#define pc __builtin_popcount
#define db double
#define pii pair<int, int>
#define fi first
#define se second
#define F(i,x,y) for (int i = (x); i <= (y); ++i)
#define D(i,x,y) for (int i = (x); i >= (y); --i)
 
using namespace std;
 
const ll inf = 1ll * 1e18;
//const ll mod = 998244353ll;
 
int n, m, x;
 
const ll mod = 1ll * 1e9 + 7ll;
 
inline void Rd(int& x) {
	int f = 1;
	x = 0;
	char c = getchar();
	while (c < '0' || c > '9') {
		if (c == '-') f = -1;
		c = getchar();
	}
	while (c >= '0' && c <= '9') x = (x << 3) + (x << 1) + (c - 48), c = getchar();
	x *= f;
}
 
inline void Wt(int x) {
	if (x < 10) {
		putchar(x + 48);
		return;
	}
	Wt(x / 10);
	putchar((x % 10) + 48);
}
 
string a, b;
string ra, rb;
//int n;
int _pos, tag;
 
int lp, rp;
 
string c;
 
bool cmp(char x, char y) {
	return x > y;
}
 
int main() {
//	OPEN
//	IOSc
 
	cin >> ra >> rb;
 
	sort (ra.begin(), ra.end());
	sort (rb.begin(), rb.end(), cmp);
 
	n = ra.size();
	a = ' ' + ra, b = ' ' + rb;
	cerr << a << '\n' << b << '\n';
	c = " ";
 
	lp = 0, rp = n + 1;
 
	F(i, 1, n << 2) c += '?';
	int flg = 0;
	F(i, 1, n) {
		if (a[i] < b[i]) {
			c[++ lp] = a[i];
			if (lp == rp || (lp + 1 == rp)) break ;
			if (i != n && a[i + 1] > b[i + 1]) c[-- rp] = b[n / 2], tag = 1;
			else c[++ lp] = b[i];
//			cerr << a[i] << ' ' << b[i] << ' ' << a[i + 1] << ' ' << c << ' '<< i << '\n';
		} else {
			if (! _pos) _pos = i;
			break ;
		}
	}
 
 
	if (_pos) {
		if (n & 1) {
			for (int i = n / 2 + 1, j = n / 2 - tag; i >= _pos; -- i,-- j) {
//				cerr << c << ' ' << a[i] << ' ' << b[j] << '\n';
				c[-- rp] = a[i];
				if (lp == rp || (lp + 1 == rp)) break ;
				c[-- rp] = b[j];
			}
//			cerr << c <<
		} else {
			for (int i = n / 2, j = n / 2 - tag; i >= _pos; -- i,-- j) {
//				cerr << c << ' ' << a[i] << ' ' << b[j] << '\n';
				c[-- rp] = a[i];
				if (lp == rp || (lp + 1 == rp)) break ;
				c[-- rp] = b[j];
			}
		}
	}
 
	F(i, 1, n) cout << c[i];
}

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