#include <iostream>
#include <cmath>
using namespace std;

#define ll long long 
int main()
{
    ll a,da,b,db;
    cin>>a>>da>>b>>db;
    int count1 = 0;
    int count2 = 0;
    while(a>0)
    {
        if(a%10==da)count1++;
        a/=10;
    }
    while (b>0)
    {
        if(b%10==db)count2++;
        b/=10;
    }
    int sum = 0;
    for(int i = 0;i<count1;i++)
    sum = sum+da*pow(10,i);
    for(int i = 0;i<count2;i++)
    sum = sum+db*pow(10,i);
    cout<<sum;
    return 0;
}