// editor5
#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 w1,w2;
    cin>>w1>>w2;
    if(!isvalid(w1) || !isvalid(w2)){
        cout<<"Invalid input";
        return 0;
    }
    string result ="";
    int i=o;
    while(i<w1.length() || i<w2.length()){
        if(i<w1.length())
        result += w1[i];
        if(i<w2.length())
        result += w2[i];
        i++
    }
    cout<<result;
    return 0;
}