Serval is a new student in Japari Kindergarten.
There is an English course in the kindergarten. The teacher sets some writing tasks for students to improve their writing skills. Therefore, Serval has to complete an essay, in English.
You might know that in an essay, the author has to convince readers of several
arguments by showing them evidence.
Serval have collected

available arguments numbered from

to

that can be written in his essay. For the

-th argument, Serval can conclude that

-th argument is true when the arguments numbered

are all true. Specially, the

-th argument cannot be proven true by making conclusion when

. It is guaranteed that

for all

(

), and

when

.
At the beginning of his essay, Serval will set exactly one argument from all the arguments as the
argument basis, which is regarded as true. Starting with the argument basis, Serval will claim that some other arguments are true by making conclusions to complete his essay. It can be shown that for the

-th argument with

, it can be true if and only if it is the argument basis.
Serval wants to maximize the number of true arguments in the essay, so he needs to set the argument basis optimally. However, as a kindergarten student, he cannot even find out the number of true arguments he can obtain.
Could you help him find out the answer?