#define _USE_MATH_DEFINES
#include  <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
#include <string>
#include<math.h>
#include<iomanip>
#include<stdio.h>
#include <stdlib.h>
#include<stdio.h>
#include <queue>
#include<map>
#include <fstream>
#include <sstream>
#include<set>
#include<stack>
#include<time.h>
#include <sys/types.h>
#include <tuple>
#include <numeric>
#include <iterator>

typedef long long int ll;
//#include<bits/stdc++.h>


using namespace std;





int main()
{

    int Q;
    Q = 1;
    //cin >> Q;


    while (Q--) {
        int n;
        cin >> n;
        string p;
        cin >> p;
        sort(p.begin(), p.end());
        for (int i = 1; i < n; i++) {
            if (p[i] == p[i - 1]) {
                cout << "No"; return 0;
            }
        }
        cout << "Yes";
    }
    return 0;
}