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

bool valid(string str){
    for(char ch : str){
        if(!isalpha(ch)){
            return false;
        }
    }
    return true;
}
int main()
{
    string word1,word2;
    cin>>word1;
    cin>>word2;
    
    if(valid(word1) || !valid(word2)){
        cout<<"Invalid input";
        return 0;
    }
    string result = "";
    int i = 0;
    
    while(i < word1.length() && i< word2.length()){
        result +=word1(i);
        result +=word2(i);
        i++;
        
    }
    while(i<word1.length()){
        result +=word(q)
        i++;
    }
     while(i<word1.length()){
        result +=word(q)
        i++;
    }
    cout<<result;
    return 0;
}