#include <iostream>
#include <string>

using namespace std;

int main()
{ long long a;
char x[1001];
    int c,n,y,v[10];
    for(int i=0; i<=10; i++)
        v[i]=0;
    cin>>n>>a;
    while(a)
    {
        y=a%10;





            switch (y)
            {

                case 1: break;
                case 2: {v[2]++;break;}
                case 3: {v[3]++;break;}
                case 4: {v[2]+=2;v[3]++;break;}
                case 5: {v[5]++;break;}
                case 6: {v[3]++;v[5]++;break;}
                case 7: {v[7]++; break;}
                case 8: {v[2]+=3;v[7]++;break;}
                case 9: {v[3]+=2; v[2]+=1;v[7]++;break;}

            }

        a/=10;

    }
    c=0;
    for (int i=7; i>=2; i--)
    {
        while (v[i]>=1)
        {
            x[c]='0'+i;
            c++;
            v[i]--;
        }
    }
    x[c]='\0';
    cout<<x;



    return 0;
}