static void Main()
{
var n = 1000000000000000000;
var fiboMatrix = new Matrix22(
1, 1,
1, 0);
Console.WriteLine(FastPower(fiboMatrix, n, Mod).UpperLeftCorner);
}
static Matrix22 FastPower(Matrix22 matrix, long p, long mod)
{
if (p == 0)
{
return(new Matrix22(1, 0, 0, 1));
}
if (p % 2 == 1)
{
return(matrix.MultiplyTo(FastPower(matrix, p - 1, mod)).ModDivide(mod));
}
return(FastPower(matrix, p / 2, mod).Square().ModDivide(mod));
}
