#include<bits/stdc++.h>
using namespace std;

int main()
{
	string s,t,ans="";
	bool found=false;
	cin>>s>>t;
	int n=s.size(),m=t.size();
	for(int i=0;i<=n-m;i++)
	{
		string ss=s;
		bool ok=true;
		for(int j=0;j<m;j++)
		{
			if(ss[i+j]=='?')
				ss[i+j]=t[j];
			else if(ss[i+j]!=t[j])
			{
				ok=false;
				break;
			}
		}
		if(ok)
		{
			for(int j=0;j<n;j++)
				if(ss[j]=='?')
					ss[j]='a';
			if(found)
			{
				if(ss<ans)
					ans=ss;
			}
			else
			{
				ans=ss;
				found=true;
			}
		}		
	}
	if(found)
		cout<<ans;
	else
		cout<<"UNRESTORABLE";
	return 0;
}