#include <iostream>
#include <vector>
#include <string>
#include <algorithm>
using namespace std;

int main() {
    int n;
    cin >> n;
    vector<int> d;
    int temp;
    while (cin >> temp) {
        d.push_back(temp);
    }
    vector<int> a(10, 0);
    string k = "";

    for (int i : d) {
        a[i] += 1;
    }

    int s = 0;
    bool x = true;
    int j;

    for (int i = 0; i < 10; ++i) {
        if (a[i] % 2 != 0) {
            s += 1;
            j = i;
            if (s > 1) {
                x = false;
                break;
            }
        } else if (a[i] == 0) {
            a[i] = -1;
        }
    }

    if (x) {
        if (a[0] == -1) {
            for (int i = 9; i >= 0; --i) {
                if (a[i] != -1) {
                    k += to_string(i) * (a[i] / 2);
                }
            }
            cout << k + to_string(j) + string(k.rbegin(), k.rend()) << endl;
        } else if (a[0] % 2 == 0) {
            a[j] -= 1;
            for (int i = 9; i >= 0; --i) {
                if (a[i] != -1 && a[i] != 0) {
                    k += to_string(i) * (a[i] / 2);
                }
            }
            if (k.length() + to_string(j).length() + k.length() == n) {
                cout << k + to_string(j) + string(k.rbegin(), k.rend()) << endl;
            } else {
                cout << "NONE" << endl;
            }
        }
    } else {
        cout << "NONE" << endl;
    }

    return 0;
}

n=int(input())
d=list(map(int,input().split()))
a=[0]*10
k=''
for i in d:
    a[int(i)]+=1
s=0
x=True
for i in range(10):
    if a[i]%2!=0:
        s+=1
        j=i
        if s>1:
            x=False
            break
    elif a[i]==0:
        a[i]=-1
if x:
    if a[0]==-1:
        for i in range(9,-1,-1):
            if a[i]!=-1:
                k=k+str(i)*(a[i]//2)
        print(k+str(j)+k[::-1])
    elif a[0]%2==0:
        a[j]-=1
        for i in range(9,-1,-1):
            if a[i]!=-1 and a[i]!=0:
                k=k+str(i)*(a[i]//2)
        if len(k+str(j)+k[::-1])==len(n):
            print(k+str(j)+k[::-1])
        else:
            print("NONE")
else:
    print("NONE")