#include<bits/stdc++.h>
#define Add(x,y) (x+y>=mod)?(x+y-mod):(x+y)
#define lowbit(x) x&(-x)
#define pi pair<ll,ll>
#define pii pair<ll,pair<ll,ll>>
#define iip pair<pair<ll,ll>,ll>
#define ppii pair<pair<ll,ll>,pair<ll,ll>>
#define fi first
#define se second
#define full(l,r,x) for(auto it=l;it!=r;it++) (*it)=x
#define Full(a) memset(a,0,sizeof(a))
#define open(s1,s2) freopen(s1,"r",stdin),freopen(s2,"w",stdout);
#define For(i,l,r) for(int i=l;i<=r;i++)
#define _For(i,l,r) for(int i=r;i>=l;i--)
using namespace std;
typedef double db;
typedef unsigned long long ull;
typedef long long ll;
bool Begin;
inline ll read(){
    ll x=0,f=1;
    char c=getchar();
    while(c<'0'||c>'9'){
        if(c=='-')
          f=-1;
        c=getchar();
    }
    while(c>='0'&&c<='9'){
        x=(x<<1)+(x<<3)+(c^48);
        c=getchar();
    }
    return x*f;
}
inline void write(ll x){
	if(x<0){
		putchar('-');
		x=-x;
	}
	if(x>9)
	  write(x/10);
	putchar(x%10+'0');
}
ll n;
string a,b;
bool check(ll x,ll y){
	if(x==4&&y==7)
	  return 0;
	return x<y;
}
bool End;
int main(){
	cin>>a>>b;
	if(a.size()^b.size()){
		if(a.size()>b.size())
		  printf("%s\n",a.c_str());
		else
		  printf("%s\n",b.c_str());
	}
	else{
		n=a.size();
		For(i,0,n-1){
			if(a[i]^b[i]){
				if(check(a[i]-'0',b[i]-'0'))
				  printf("%s\n",b.c_str());
				else
				  printf("%s\n",a.c_str());
				exit(0);
			}
		}
		printf("%s\n",a.c_str());
	}
	return 0;
}