#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 10;
const int M = 1e9 + 7;
const int MOD = 998244353;
const double PI = 3.141592653589793238460;
long long int power(long long int a, long long int b) {
  long long int res = 1;
  if (a == 0) return 0;
  if (a == 1) return 1;
  for (; b > 0; b >>= 1) {
    if (b & 1) res = (res * a);
    if (res > MOD) res %= MOD;
    a = (a * a);
    if (a > MOD) a = a % MOD;
  }
  return res;
}
bool isPrime[1000001];
vector<long long int> prime;
void seive(int limit) {
  isPrime[0] = isPrime[1] = 1;
  for (int i = 2; i * i <= limit; i++) {
    if (!isPrime[i])
      for (int j = i * i; j <= limit; j += i) {
        isPrime[j] = 1;
      }
  }
  for (int i = 2; i <= limit; i++)
    if (!isPrime[i]) prime.push_back(i);
}
int main() {
  string n, s;
  cin >> n >> s;
  sort(s.rbegin(), s.rend());
  int j = 0;
  for (int i = 0; i < n.length(); i++) {
    if (n[i] < s[j]) {
      n[i] = s[j];
      j++;
      if (j == s.length()) break;
    }
  }
  cout << n;
}
