// editor5
#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;
    cin>>word1>>word2;
    if(!isValid(word1)||!isValid(word2)){
        cout<,"Invalid input";
        return 0;
    }
    string result ="";
    int i=0;
    while (i<word1.length()||i<word2.length()){
        if(i<word1,length())
        result+=word1[i];
        if(i<word2,length())
        result+=word2[i];
        i++;
    }
    cout<<result;
    return 0;
}