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

bccdb
 z
 dfdeed
 aab
 y
 abac

var j = readline().split('');
var cd = readline().split('');
var aj= j.sort();
var d = cd.sort().reverse();
var c = ''
for(var is=0;is<j.length/2;is++)
{
   c+=aj[is]+d[is]
    
}
 
if(j.join('')!==cd.join(''))
print(c.replace(c[c.length-1],''))
else
print(c)