#include<iostream>
#include<string>
#inclde<cctype>
using namespace std;
boolisValid(string s){
    for(char ch:s){
        if(!isalpha(ch))
        return false;
    }
    return true;
}
int main(){
    string word1, word2;
    getline(cin,word1);
    getline(cin,word2);
    
    if(word1.empty()|| word2.empty()||!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++;
    }
    result += word1.substr(i);
    result += word2.substr(i);
    cout<<result;
    return 0;
}