#include <bits/stdc++.h>
#define ill int long long
#define pb push_back
#define fi first
#define se second
#define ld long double
using namespace std;
int l,r,mid,n,m,i,j,mod=1e9+7,p[400006],h[400006],h1[400006];
string s,t,ans,s1;
bool check(int l)
{
    if (l==0)return 1;
    set<int> q;
    int i;
    for (i=l;i<=n;i++)
    {
        int x=(h[i]-h[i-l])/p[i-l+1];
        if (x<0)x+=mod;
        q.insert(x);
    }
    for (i=l;i<=m;i++)
    {
        int x=(h1[i]-h1[i-l])/p[i-l+1];
        if (x<0)x+=mod;
        if (q.find(x)!=q.end())return 1;
    }
    return 0;
}
int main()
{
    ios_base::sync_with_stdio(0);cin.tie(NULL);cout.tie(NULL);
    cin>>s>>t;
    n=s.size();
    m=t.size();
    p[1]=1;
    for (i=2;i<=max(n,m);i++)
        p[i]=(p[i-1]*19)%mod;
    for (i=1;i<=n;i++)
    {
        h[i]+=p[i]*(s[i-1]-'a')+h[i-1];
        h[i]%=mod;
    }
    for (i=1;i<=m;i++)
    {
        h1[i]+=p[i]*(t[i-1]-'a')+h1[i-1];
        h1[i]%=mod;
    }
    l=0;r=min(n,m);
    while (l+1<r)
    {
        mid=(l+r)/2;
        if (check(mid))l=mid;
        else r=mid;
    }
    if (check(r))l=r;
    if (l==0)return 0;
    set<int> q;
    for (i=l;i<=n;i++)
    {
        int x=(h[i]-h[i-l])/p[i-l+1];
        if (x<0)x+=mod;
        q.insert(x);
    }
    for (i=l;i<=m;i++)
    {
        int x=(h1[i]-h1[i-l])/p[i-l+1];
        if (x<0)x+=mod;
        if (q.find(x)!=q.end())
        {
            int h=1;
            s1="";
            for (j=i-l;j<l;j++)
            {
                if (h==1 && (ans.size()>0 && t[j]<ans[j-(i-l)]))h=0;
                if (h==1 && (ans.size()>0 && t[j]>ans[j-(i-l)])){h=2;break;}
                s1+=t[j];
            }
            if (ans=="" || h==0)
                ans=s1;
        }
    }
    cout<<ans;
}