#include<iostream>
#include<string>
#include<cctype>

using namespace std;
bool isValid (const string&s){
    if(s.empty ()) return true;
    for(char c:s){
        if(!isalpha (c)){
            return false;            
        }
       
    }
    return true;
}
int main(){
    string word1,word2;
    if(!(cin>>word1)) return 0;
    if(!(cin>>word2)) return 0;
    if(!isValid(word1)) || !isValid(word2)){
        cout<<"Invalid input"<<endl;
        return 0;
    }
    string merged="";
    int i=0,j=0;
    int n1=word1.length();
    int n2=word2.length();
    while(i<n1 || j<2){
        if(i<n1){
            merged+=word1[i++];
        }
        if(j<n2){
            merged+=word2[j++];
    }
    }
    cout<<merged<<endl;
    return 0;
    
    
}