#include<iostream>
#include<string>
#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>>word 1>>word2;
        
        if(!isValid(word1) || !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;
    
}