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