#include<iostream>
#include<string>
#include<cctype>
using namespace std;

int main()
{
    string w1,w2;
    cin>>w1>>w2;
    for(char c:w1)
    if(!isalpha(c))
        {
            cout<<"Invalid input";
            return 0;
        }
    
    for(char c:w2)
    if(!isalpha(c))
        {
            cout<<"Invalid input";
            return 0;
        }
        //string res="";
        uint n=max(w1.length(),w2.length());
        
        for(int i=0;i<n;i++)
        {
            if(i<w1.length()res+=w1[i]);
            if(i<w2.length()res+=w2[i]);
        }
        cout<<res;
        return 0;
}