bcdef
abbbc
 z
y
 reddit
abcdef
 abc
aaa
 y
z
 cbxz
aaaa

bccdb
 z
 dfdeed
 aab
 y
 abac

import sys

def main():
    s=sys.stdin.readline().rstrip()
    t=sys.stdin.readline().rstrip()
    
    result=[]
    
    iis=0
    iit=0
    
    aas=list(sorted(list(s)))
    aat=list(sorted(list(t),reverse=True))
    
    for i in range(len(s)):
        if i%2==0:
            result.append(aas[iis])
            iis+=1
        else:
            result.append(aat[iit])
            iit+=1
    
    sys.stdout.write(''.join(result)+'\n')
    
main()

