#include<iostream>
#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;
    cin>>word2;
     if(!isvalid(word1) || !isvalid(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;
}