#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<word1.length()){
            result+=word1[i];
            
        }
        if(i<word2.length()){
            result+=word2[i];
            i++;
        }
    }
    cout<<result;
    return 0;
}