#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

var n = I<int>();
var a = I<int>();
var b = I<int>();
var ans = 0;
for (var i = 1; i <= n; i++) if (i % a > i % b) ans++;
Console.WriteLine(ans);