Input Format

The first line of input contains a single integer n (1n55) the number of pathways. Each of the following n lines contains two integers xi and yi (1xi,yi1000) the coordinates of the i-th pathway. Note that the north direction coinides with the direction of y axis, so the east direction coinides with the direction of the x axis. All pathways locations are distinct.

Constraints

n (1n55) (1xi,yi1000)

Output Format

Output the minimal number of pathways that need to be created in order for Zahir to be able to reach any pathway from any other one.

Sample Input 0

2 2 1 1 2

Sample Output 0

1

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