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

bool valiod(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,j = 0;
    while(i < word1.length() || j < word2.length(){
       if(i < word1.length()  result += word1[i++];
       if(j < word2.length()  result += word2[j++];
    }
    cout<<result;
    return 0;
}