#include<bits/stdc++.h>
#define LL long long
#define LLL __int128
#define uint unsigned
#define ldb long double
#define uLL unsigned long long
using namespace std;
signed main(){
    cin.tie(0)->sync_with_stdio(0);
    string s,t;
    cin>>s>>t;
    int l=t.find('1');
    if(l!=t.npos){
        string d=s.substr(l);
        int n=d.length();d=" "+d;
        vector<int>nxt(n+1);
        nxt[1]=n;
        for(int i=2,j=0,k=0;i<=n;++i){
            nxt[i]=max(min(k-i,nxt[i-j+1]),0);
            for(;i+nxt[i]<=n&&d[nxt[i]+1]==d[i+nxt[i]];++nxt[i]);
            if(i+nxt[i]>k)j=i,k=i+nxt[i];
        }
        int m=n;
        for(int i=0;i<n;++i)if(t[l+i]&1)m=min(m,nxt[i+1]);
        d=s.substr(l,m),d=" "+d;
        n=s.length(),s=" "+s;
        nxt.resize(m+1),nxt[1]=0;
        for(int i=2,j=0;i<=m;++i){
            for(;j&&d[j+1]!=d[i];j=nxt[j]);
            nxt[i]=(j+=(d[j+1]==d[i]));
        }
        for(int i=1,j=0;i<=n;++i){
            for(;j&&d[j+1]!=s[i];j=nxt[j]);
            if(d[j+1]==s[i])++j;
            if(i>=m&&(t[i-m]&1)!=(j==m))return cout<<"-1\n",0;
            if(j==m)j=nxt[j];
        }
        cout<<d.substr(1)<<'\n';
    }
    else cout<<s+"a"<<'\n';
    return 0;
}
/*

*/