#include<bits/stdc++.h>
#define x first
#define y second
#define PB push_back
#define mst(x,a) memset(x,a,sizeof(x))
#define all(a) begin(a),end(a)
#define rep(x,l,u) for(ll x=l;x<u;x++)
#define rrep(x,l,u) for(ll x=l;x>=u;x--)
#define IOS ios::sync_with_stdio(false);cin.tie(0);
using namespace std;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef pair<long,long> PLL;
typedef pair<char,char> PCC;
typedef long long ll;
const int N=5010;
const int M=1e6+10;
const int INF=0x3f3f3f3f;
const int MOD=1e9+7;
int cnt[10];
void solve(){
int n;cin>>n;
string s;cin>>s;
rep(i,0,n){
int u=s[i]-'0';
if(u==4){
cnt[2]+=2;
cnt[3]++;
}else if(u==6){
cnt[5]++;
cnt[3]++;
}else if(u==8){
cnt[7]++;
cnt[2]+=3;
}else if(u==9){
cnt[7]++;
cnt[3]+=2;
cnt[2]++;
}
}else{
cnt[u]++;
}
}
while(cnt[7]--) cout<<7;
while(cnt[5]--) cout<<5;
while(cnt[3]--) cout<<3;
while(cnt[2]--) cout<<2;
cout<<endl;
}
int main(){
IOS;
//int t;cin>>t;
//while(t--){
solve();
//}
return 0;
}