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

typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
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;

int main(){
    int n;
    cin >> n;
    vector<int> a(n);
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
    }
    sort(all(a));
    for (int i = 1; i < n; ++i) {
        if (a[i] == a[i-1]){
            cout << "NO" << endl;
            return 0;
        }
    }
    cout << "YES" << endl;
}
#include <bits/stdc++.h>
using namespace std;
#define ff        first
#define ss        second
#define ll        long long
#define int       long long
#define inf       ((ll)1e18)
#define mod       1000000007
#define double    long double
#define ull       unsigned long long
#define vi        vector<ll>
#define ppi       pair<int,int>
#define pii       pair<pair<int,int>,int>
#define pb        push_back
#define pi        2*acos(0.0)
#define rev       greater<int>()
#define pr(a,x,y) for(int i=x;i<y;i++){cout<<a[i]<<" ";}
#define ps(s)     for(auto i:s){cout<<i<<" ";}
#define sp(x,y)   fixed<<setprecision(y)<<x
#define w(x)      ll x; cin>>x; while(x--)
#define all(v)    v.begin(), v.end()
#define rall(v)   v.rbegin(), v.rend()
#define test      cout<<"This is test"<<endl;
#define str       string
#define endl      '\n'
#define e         cout<<'\n';
void kehsihba(){
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	/*#ifndef ONLINE_JUDGE
		freopen("input.txt", "r", stdin);
		freopen("output.txt", "w", stdout);
	#endif*/
}
void solve(){
	ll n;cin>>n;
	ll x;
	set<int>s;
	for(int i=0;i<n;i++){
		cin>>x;s.insert(x);
	}
	cout<<(((int)s.size()==n)?"YES":"NO");
}
int32_t main(){
	kehsihba();
	//init();
	ll t=1;
	//cin>>t;
	for(int k=1;k<=t;k++){
		//cout<<"Case "<<k<<": ";
		solve();
		//e;
	}
}
