// O(log n)
public static long GetValueWithMod(long n, long mod)
{
var m = new ModMatrixOperator(mod);
var a = new long[2, 2];
a[0, 0] = a[0, 1] = a[1, 0] = 1;
a = m.Pow(a, n);
var v = m.Mul(a, new[] { 1L, 2 });
return(v[1]);
}
// O(log n)
public static long GetValueWithMod(long p, long q, long r, long a0, long a1, long a2, long n, long mod)
{
var m = new ModMatrixOperator(mod);
var a = new long[3, 3];
a[0, 0] = p;
a[0, 1] = -q;
a[0, 2] = r;
a[1, 0] = a[2, 1] = 1;
a = m.Pow(a, n);
var v = m.Mul(a, new[] { a2, a1, a0 });
return(v[2]);
}