#include<bits/stdc++.h>
#define ld long double
#define int long long
#define all(v) v.begin(),v.end()
#define allr(v) v.rbegin(),v.rend()
using namespace std;
void solve(){
    string s,t;
    cin>>s>>t;
    map<char,vector<int>>mp;
    int n=s.length(),m=t.length();
     for (int i=0;i<m;i++) {
         mp[t[i]].push_back(i);
     }
    int x=0,inds=-1,indt=-1;
    for (int i=0;i<n;i++) {
          if (!mp[s[i]].empty()) {
               int l=0,r=mp[s[i]].size()-1;
                vector<int>v=mp[s[i]];

              while (l<=r) {
                  int mid=(l+r)/2;
                   int sz=m-v[mid];
                  if (sz+i>=3&&(i!=0&&sz!=2)) {
                      indt=v[mid];
                      l=mid+1;
                  }else r=mid-1;
              }
              if (indt!=-1) {
                  inds=i;
                  break;
              }
          }
    }
    if (inds==-1||indt==-1) {
        cout<<"-1\n";
        return;
    }
    string ans=s.substr(0, inds);
    ans+=t.substr(indt, m);
     cout<<ans<<"\n";
}
int32_t main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int t=1;
    //cin>>t;
    while(t--){
        solve();
    }
}