// editor5
#include<iostream>
#include<string>
using namespace std;
int main(){
    string word1 ,word2;
    cin>>word1>>word2;
    for(int i=0;i<word1.length();i++){
        char c=word1[i];
        if(!(c>='a'&&c<='z')||(c>='A'&&c<='Z')){
            cout<<"Invalid input"<<endl;
            return 0;
        }
    }
    for(int i=0;i<word2.length();i++){
        char c=word2[i];
        if(!(c>='a'&&c<='z')||(c>='A'&&c<='Z')){
            cout<<"Invalid input"<<endl;
            return 0;
        }
     i=0;
    while(i<word1.length()||i<word2.length()){
        if(int i<=world1.length()){
            cout<<word1[i];
        }
        if(i<world2.length()){
            cout<<word2[i];
        }
        i=i+1;
    }
    cout<<endl;
    return 0;
}