#include <iostream>
#include<string>
#include<map>
using namespace std;

int main(){
  string s; cin >> s;
  int check[26] = {};
  for(int i = 0; i < s.size(); i++){
    int t = s[i]-'a';
    check[t] = 1;
  }
  for(int i = 0; i < 26; i++){
    if(check[i] == 0) { 
      char ans = 'a' + i;
      cout << ans << endl;
      return 0;
    }
  }
  cout << "None" << endl;
  return 0;
}

#include <iostream>

using namespace std;

int harshad(int n)  {
    int res = 0;
    while (n > 0)   {
        res += n % 10;
        n /= 10;
    }
    return res;
}

int main()  {
    int n;
    cin >> n;
    int sum_of_digits = harshad(n);
    if (n % sum_of_digits == 0) {
        cout << "Yes" << endl;
    } else {
        cout << "No" << endl;
    }
    return 0;
}