#include<iostream>
#include<string>
#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>>word2;
    if(!isvalid(word1)||!isvalid(word2)){
        cout<<"Invalid input";
        return 0;
    }
    string result=" ";
    int i=0;
    while(i<word1.length()|| i<word2.length()){
        if (i<word.length());
        result +=word1[i];
        if(i<word2.length());
        result +=word2[i];
        i++
        }
        cout<<result;
        return 0;
}