#include <iostream>
#include <string>
#include <cctype>
#include <vector>

using namespace std;

int main() {
    freopen("input.txt.txt", "r", stdin);
    freopen("output.txt", "w", stdout);

    string letters = "abcdefghijklmnopqrstuvwxyz";
    string s;
    vector<int> a(26);
    for(int i = 0; i < a.size(); ++i)
        a[i] = 0;
    for(auto x : a)
        cout << x;
    int n;
    cin >> n;
    cin >> s;
    if (n < 26) {
        cout << "NO";
        return 0;
    }
    else
        for(int i = 0; i < n; i++)
            if (isupper(s[i]))
                s[i] = tolower(s[i]);
            for(int i = 0; s[i]; ++i)
                if(letters.find(s[i]))
                    a[122 - int(s[i])] = 1;
                for(auto x : a)
                    cout << x;

}