public override IEnumerable <object> Solve(TextReader inputStream)
{
var n = inputStream.ReadInt();
var s = inputStream.ReadLine();
if (s[0] == 'W' || s[^ 1] == 'W')
{
yield return(0);
yield break;
}
var edges = new Edge[s.Length];
var last = s[0];
for (int i = 1; i < s.Length; i++)
{
if (s[i] != last)
{
edges[i] = edges[i - 1];
}
else
{
edges[i] = edges[i - 1] == Edge.Left ? Edge.Right : Edge.Left;
}
last = s[i];
}
if (edges.Count(e => e == Edge.Left) != n)
{
yield return(0);
yield break;
}
var count = Modular.One;
var leftCount = 0;
foreach (var edge in edges)
{
if (edge == Edge.Left)
{
leftCount++;
}
else
{
count *= leftCount--;
}
}
count *= Modular.Factorial(n);
yield return(count);
}
public override IEnumerable <object> Solve(TextReader inputStream)
{
var nm = inputStream.ReadIntArray();
var dogs = nm[0];
var monkeys = nm[1];
if (dogs == monkeys)
{
yield return((Modular.Factorial(dogs) * Modular.Factorial(monkeys) * new Modular(2)).Value);
}
else if (Math.Abs(dogs - monkeys) <= 1)
{
yield return((Modular.Factorial(dogs) * Modular.Factorial(monkeys)).Value);
}
else
{
yield return(0);
}
}
public override IEnumerable <object> Solve(TextReader inputStream)
{
var xy = inputStream.ReadIntArray();
var x = xy[0];
var y = xy[1];
if (2 * x < y || 2 * y < x || (x + y) % 3 != 0)
{
yield return(0);
yield break;
}
var a = (2 * x - y) / 3;
var b = (2 * y - x) / 3;
var two = new Modular(2);
yield return((Modular.Factorial(a + b) / (Modular.Factorial(a) * Modular.Factorial(b))).Value);
}
