#include <bits/stdc++.h>
#include <atcoder/all>
#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    string x,y;
    cin >> x >> y;
    if(x.size()<=y.size()+1) {
        reverse(x.begin(),x.end());
        reverse(y.begin(),y.end());
        while(!y.empty()) {
            cout << x.back() << y.back();
            x.pop_back();
            y.pop_back();
        }
        if(!x.empty()) {
            cout << x << endl;
        }
        else{
            cout << endl;
        }
    }
    else{
        cout << "?" << endl;
    }
    return 0;
}