#include<bits/stdc++.h>
using namespace std;
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define all(a) begin(a),end(a)
#define allr(a) rbegin(a),rend(a)
#define UNIQUE(x) sort(all(x)), x.erase(unique(all(x)), x.end())
using ll =long long;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi= vector<int>;
using vll =vector<ll>;
using vvi = vector<vector<int>>;
inline bool ingrid(int a,int b,int h,int w){
    return 0<=a&&a<h&&0<=b&&b<w;
}
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
int popcount(int t){return __builtin_popcount(t);}
int popcount(ll t){return __builtin_popcountll(t);}
struct Edge{
    int from,to;ll cost;int idx;
    Edge()=default;
    Edge(int from,int to,ll cost=1,int idx=-1):from(from),to(to),cost(cost),idx(idx){}
    operator int() const {return to;}
};


constexpr pii dx4[4]={{0,1},{0,-1},{1,0},{-1,0}};
constexpr pii dx[100]={};
#define endl '\n'
int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    string x,y;cin>>x>>y;
    string ans(300,'#');
    int len=0;
    rep(i,0,x.size()){
        ans[2*i]=x[i];
        chmax(len,2*i);
    }
    rep(j,0,y.size()){
        ans[2*j+1]=y[j];
        chmax(len,2*j+1);
    }
    string tmp;
    rep(i,0,len+1){
        tmp.push_back(ans[i]);
        if(ans[i]=='#'){
            cout<<'?'<<endl;
            return 0;
        }
    }
    
    cout<<tmp<<endl;

    return 0;
}