Modular combination(Modular n, Modular r)
{
Modular a = 1;
Modular b = 1;
for (int i = 1; i <= (int)r; i++)
{
a = (n - i + 1) * a;
b = b * i;
}
return(a * Modular.Pow(b, MOD - 2));
}
public static Modular Pow(Modular a, int n)
{
switch (n)
{
case 0:
return(1);
case 1:
return(a);
default:
var p = Pow(a, n / 2);
return(p * p * Pow(a, n % 2));
}
}
public void Solve()
{
Cin(out N);
Cin(out A);
var diff = new List <Modular>();
int before = 0;
int mcount = 0;
for (int i = 0; i < N; i++)
{
if (A[i] == -1)
{
mcount++;
continue;
}
if (mcount > 0)
{
int k = A[i] - before;
if (k > 0)
{
diff.Add(combination(k + mcount, mcount));
}
mcount = 0;
}
before = A[i];
}
Modular ans = 1;
foreach (Modular t in diff)
{
ans = ans * t;
}
Console.WriteLine((int)ans);
}
