#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0)

#define Yes cout << "Yes\n"
#define No cout << "No\n"
#define YES cout << "YES\n"
#define NO cout << "NO\n"
#define fori(x,y) for(int i=(x);i<=(int)(y);++i)
#define forj(x,y) for(int j=(x);j<=(int)(y);++j)
#define fork(x,y) for(int k=(x);k<=(int)(y);++k)

#define debug(x) cerr << #x << " = " << x << endl

typedef long long ll;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;

ll MOD = 998244353;
ll qpow(ll a,ll p) {ll res=1; while(p) {if (p&1) {res=res*a%MOD;} a=a*a%MOD; p>>=1;} return res;}

vector<int> z_function(const string& s) {
    int n = (int)s.length();
    vector<int> z(n);
    for (int i = 1, l = 0, r = 0; i < n; ++i) {
        if (i <= r && z[i - l] < r - i + 1) {
            z[i] = z[i - l];
        }
        else {
            z[i] = max(0, r - i + 1);
            while (i + z[i] < n && s[z[i]] == s[i + z[i]]) ++z[i];
        }
        if (i + z[i] - 1 > r) l = i, r = i + z[i] - 1;
    }
    return z;
}

void solve() {
	string str;
    cin >> str;
    string p;
    cin >> p;
    int n = str.length();
    int pos = -1;
    for (int i=n-1;i>=0;--i) {
        if (p[i] == '1') {
            pos = i;
            break;
        }
    }
    if (pos == -1) {
        cout << str << "a" << endl;
        return;
    }
    string pre = str.substr(pos);
    string zz = pre+"#"+str;
    vector<int> z = z_function(zz);

    int ma = pre.length(), mi = 0;
    fori(pre.length()+1, zz.length()-1) {
        int j = i-pre.length()-1;
        // debug(z[i]);
        if (p[j] == '0') mi = max(mi, z[i]);
        else ma = min(ma, z[i]);
    }
    // debug(ma);
    // debug(mi);
    if (ma<=mi) cout << -1 << endl;
    else cout << pre.substr(0, mi+1) << endl;
}

signed main() {
	IOS;
	int t = 1;
	// cin >> t;
	while (t--) {
		solve();
	}
	return 0;
}