#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 word1, word2;
    getline(cin, word1);
    getline(cin, word2);
    
    if(!isValid(word1)) || !isValid(word2)) {
        cout<<"Invalid input";
        return 0;
    }
    
    string result = " ";
    int i=0;
    
    while(i<word1.length() && i<word2.length()){
        result += word1[i];
        result += word2[i];
        i++;
    }
    
    result+=word1.substr(i);
    result+=word2.substr(i);
    
    cout<<result;
    return 0;
}