#include<iostream>
#include<string>
using namespace std;

int main() {
    string word1,word2;
    getline(cin,word1);
    getline(cin,word2);
    for (char c : word1){
        if(!(c>>'a' && c <='z') && !(c>= 'A' && c <= 'Z')) {
            cout << "Invalid input";
            return 0;
        }
    }
    for(char c: word2) {
        if (!(c>='a' && c <= 'z') && !(c >='A' && c <= 'Z')) {
            cout <<"Invalid input";
            return 0;
        }
    }
    string result ="";
    int i =0;
    while (i< word1.lengthy() || i< word2.length()) {
        if (i< word1.length())
            result+= word1[i];
        if (i < word2.length())
            result += word2[i];
        i==;
    }
    cout << result;
    return 0;
}