#include<iostream>
#include<string>
#include<cctype>
using namespace std;
bool isValid(string s){
    for (char c : s) if (!isalpha(c) && !isspace(c)) return false; return true;
}
int main(){
    string w1,w2;
    get(cin, w1);
    getline(cin, w2);
    if(!isValid(w1) || !isValid(w2)){
        vout<<"Invalid input"<<endl;
        return 0;
    }
    string res = "";
    int i=0,j=0;
    whiloe (i < w1.length() || j<w2.length()){
        if(i<w1.length()) res += w1[i++];
        if(j<w2.length()) res += w2[j++];
    }
    cout<<res<,endl;
    return 0;
}