#nullable enable

#region
var _input = Array.Empty<string>();
var _iter = 0;
string String()
{
    while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Split(' '), 0);
    return _input[_iter++];
}
T I<T>() where T : IParsable<T> => T.Parse(String(), null);
#endregion

T[] Range<T>(int n, Func<T> F) => Enumerable.Range(0, n).Select(_ => F()).ToArray();

var n = I<int>();
var az = Range(n, I<int>);
var max = az.Max();

Console.WriteLine(max > 0 ? "Yes" : "No");