#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>> word1>> word2;
    if(!isValid(word1)||!isValid(word2)){
        cout<< "Invalid input";
        return 0; 
        
    }
    string result ="";
    int i=0,j=0;
    while (i<word1.length() || i<word2.length()){
        if(i< word1.length()){
          result+=word1[i++];
        }
        if(j< word2.length()){
          result+=word2[j++];
        }
        
    }
    cout<<result;
    return 0;
}