#nullable enable

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

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

var n = I<int>();
var ans = true;
var d = new Dictionary<int, int>();
for (var i = 0; i < n; i++)
{
    var s = I<int>();
    var t = I<int>();
    if (d.TryGetValue(s, out var ct) && t != ct) ans = false;
    else d[s] = t;
}
Console.WriteLine(ans ? "Yes" : "No");