#include <iostream>
using namespace std;

int main() {
    string a,b;
    cin>>a>>b;
    for(char c:a)
    if(!isalpha(c)) {
        cout << "Invald input";
           return 0;
    }
    for(char c:b)
    if(!isalpha(c)) {
        cout<<"Invalid input";  
        return 0;
    }
    int 1=0;
    while(i<a.size()&&<b.size())
        cout<<a[i]<<b[i++];
    cout<<a.substr(i)<<b.substr(i);
}