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

bool isValid(string s){
    if(s.length()==0) return false;
    
    for(int i=0; i<s.length(); i++){
        if(!isalpha(s[i])){
            return false;
        }
    }
    return true;
}

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