#include<iostream>
#include<string>
using namespace std;
bool valid(string str)
{
    for(char ch:str)
    {
        if(!isalpha(ch))
        {
            return false;
        }
    }
    return true;
}
int main()
{
    string word1, word2;
    getline(cin,word1);
    getline(cin,word2);
    if(!valid(word1)||!valid(words2))
    {
        cout<<"Invalid input";
        return 0;
    }
    string result= "";
    int i=0;
    while(i<word1.lenght() && i<word2.lenght())
    {
        result+=word1[i];
        result+=word2[i];
        i++;
    }
}