#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;
    cin>>word1;
    cin>>word2;
    
    if(!valid(word2) || !valid(word2)){
        cout<<"Invalid input";
        return 0;
    }
    string result = "";
    int i = 0;
    
    while(i < word1.length()  || !valid(word2)){
        result += word1[i];
        result += word2[i];
        i++;
    }
    while(i<word1.length[i]);
    result += word1[i];
    i++
    
    }while(i<word2.lenght()){
        result += word2[i];
        i++;
    }
    cout<<result;
    return 0;
}