There are $2N$ people standing in a row, and the person at the $i$-th position from the left is wearing clothes of color $A_i$. Here, the clothes have $N$ colors from $1$ to $N$, and exactly two people are wearing clothes of each color.

Find how many of the integers $i=1,2,\ldots,N$ satisfy the following condition:

-   There is exactly one person between the two people wearing clothes of color $i$.

The input is given from Standard Input in the following format:

```
$N$
$A_1$ $A_2$ $\ldots$ $A_{2N}$
```

Print the answer.

-   $2 \leq N \leq 100$
-   $1 \leq A_i \leq N$
-   Each integer from $1$ through $N$ appears exactly twice in $A$.
-   All input values are integers.

2

There are two values of $i$ that satisfy the condition: $1$ and $3$.

In fact, the people wearing clothes of color $1$ are at the 1st and 3rd positions from the left, with exactly one person in between.

0

There may be no $i$ that satisfies the condition.