#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define REP(i, a, b) for(int i = a; i < b; i++)
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define fi first
#define se second
#define debug(x) cerr <<__LINE__<< ": " <<#x<< " = " << x << endl
#define debug_vec(v) cerr<<__LINE__<<": "<<#v<<" = ";rep(i,v.size())cerr<<" "<<v[i];cerr<<endl
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
const int INF = (1<<30) - 1;
const ll LINF = (1LL<<60) - 1;

void solve() {
    int n;
    cin >> n;
    vector<int> A(n);
    for (auto &a : A) cin >> a;
    sort(all(A));
    A.erase(unique(all(A)), A.end());
    if (n == (int)A.size()) {
        cout << "YES" << endl;
    } else {
        cout << "NO" << endl;
    }
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    solve();
    return 0;
}

#include<bits/stdc++.h>
using namespace std;

typedef long long ll;
const int INF = 1e9;
const ll LINF = 1e18;
const int mod = 1e9+7;

#define pi pair<int,int>
#define pl pair<lld,lld>

#define dump(x) cout << #x << " = " << (x) << endl
#define YES(n) cout << ((n) ? "YES" : "NO"  ) << endl
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define SANKOU(n,a,b) cout << ((n) ? (#a) : (#b) ) << endl

#define mem0(x) memset(x,0,sizeof(x))
#define fillnum(x,n) fill(begin(x),end(x),n)
#define asort(x) sort(x.begin(),x.end())
#define dsort(x,t) sort(x.begin(),x.end(),greater<t>())
#define vuniq(x) x.erase(unique(x.begin(), x.end()), x.end())

#define pb(a) push_back(a)
#define mp(a,b) make_pair(a,b)

int main() {
    string S;
    cin >> S;
    if(S.size() == 3){
        reverse(S.begin(),S.end());
        cout << S << endl;
    } else {
        cout << S << endl;
    }
}