brdpy

B.rd.py

a = list(input())
b = list(input())
changed = 1

def max(arr):
    m = '0'
    k = 0
    for i,j in enumerate(arr):
        if m < j:
            m = j
            k = i
    return (k, m)

for i,j in enumerate(a):
    if changed:
        (m,k) = max(b)
    if k > j:
        a[i] = k
        b[m] = '0'
        changed = 1;
    else:
        changed = 0

print("".join(a))