#include <bits/stdc++.h>

using namespace std;

using i64 = long long;

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

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int T = 1;
    // cin >> T;
    while (T--) {
        solve();    
    }
    return 0;
}