#include<bits/stdc++.h>

using namespace std;
typedef long long ll;
typedef double db;
const int N = 2005 + 5;
const int mod = 1e9+7;


void solve() {
    int n;
    cin>>n;
    vector<ll> a(n+1);
    for(int i=1;i<=n;i++) cin>>a[i];
    ll cnt=a[1];
    for(int i=2;i<=n;i++){
        if(cnt<=0){
            cout<<"No\n";
            return;
        }
    }
    cout<<"Yes\n";
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
//    cout<<fixed<<setprecision(7);
    int T = 1;
//    cin >> T;
    while (T--) solve();
    return 0;
}