#include <iostream>
#include <string>
using namespace std;
bool isValid(string s){
    for(int i = 0; i<str.length(); i++){
        char ch = s[i];
        if(!(ch>='A' && ch<= 'Z') || (ch>='a' && ch<='z')){
            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() && word2.length()){
        result += word1[i];
        result += word2[i];
        i++;
    }
    while(i<word1.length()){
        result += word1[i++];
    }
    while(i<word2.length()){
        result += word2[i++];
    }
    cout<<result;
    return 0;
    
}