#include <iostream>
using namespace std;
int main()
{
int n,i=0,ar[200],temp;
long long a;
cin>>n>>a;
while(n--)
{
int t=a%10;
a=a/10;
switch(t)
{case 2: ar[i]=2;
i++;
break;
case 3: ar[i]=3;
i++;
break;
case 4: ar[i]=3;
i++;
ar[i]=2;
i++;
ar[i]=2;
i++;
break;
case 5: ar[i]=5;
i++;
break;
case 6: ar[i]=5;
i++;
ar[i]=3;
i++;
break;
case 7: ar[i]=7;
i++;
break;
case 8: ar[i]=7;
i++;
ar[i]=2;
i++;
ar[i]=2;
i++;
ar[i]=2;
i++;
break;
case 9: ar[i]=7;
i++;
ar[i]=3;
i++;
ar[i]=3;
i++;
ar[i]=2;
i++;
break;
default: break;
}}
for(int j=0;j<i;j++)
{
for(int h=j+1;h<i;h++)
{
if(ar[h]>ar[j])
{
temp=ar[j];
ar[j]=ar[h];
ar[h]=temp;
}
}
cout<<ar[j];
}
return 0;
}
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