// editor5
#include<iostream>
#include<cctype>
using namespace std;
bool isvalid(string s)
{
    for(char c:s)
    {
        if(!isalpha(c))
        {
            return false;
        }
    }
    return true;
}
int main()
{
    string word1,word2;
    cin>>word1;
    cin>>word2;
    if(!usvalid(word1)||!isvalid(word2))
    {
        cout<<"Invalid input";
        return o;
    }
    string result="";
    int i=0,j=0;
    while(i<word1.length()||j<word2.length())
    {
        if(i<word1.length())
        {
            result+=word1[i++];
        }
        if(j<word2.length())
        {
            result+=word2[j++];
        }
    }
    cout<<result;
    return 0;
}