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

bool valid(string str){
    for(char ch:str){
        if(!isapha(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()&&<word2.length()){
        result += word1[i];
        result += word2[i];
        i++;
        
    }
    while(i<word1.length()){
            result += word1[i];
            i++;
            
        
    }
    while(i<word2.length()){
         result += word2[i];
            i++;
        
    }
    cout<<result;
    return 0;
        
        
}