check mapping

#include <iostream>

using namespace std;

int n,BG[100010];

int main(){
    int temp;
    cin >> n ;
    for( int i = 0 ; i < n ; i++ ){
        cin >> temp ;
        if( temp >= 0 && temp <= 100000)
            BG[temp] = 1 ;
    }

    for( int i = 1 ; i <= n ; i++ )
        if( BG[i] == 0 ){
            cout << "NO" << endl ;
            return 0;
        }
    cout << "YES" << endl;
    return 0;
}