/* 	ESC101 : Fundamental of Computing Lab 6 for 10th September 2008
	
	Two numbers a and b are said to be relatively prime ( also called coprime) if gcd(a; b) = 1.
	For a given n write a JAVA program to nd the number of coprimes less than n. For example, if n = 9, 
	then the output should be 6 since the coprimes of 9 less than 9 are 1; 2; 4; 5; 7 and 8.
	You should design and use a method called gcd which takes two integer arguments and returns their gcd.

*/

class RelPrime
{
	//Method to calculate GCD of two numbers.
    public static int gcd(int a, int b)
    {
		int t;
		while(b != 0){
	    	t = b;
	    	b = a % b;
	    	a = t;
		}
		return a;
    }

    public static void main(String args[])
    {
		int n;
		int gcd;
		int i,prime_cnt = 0;
		if(args.length==0)
			System.out.println("Please give a numeric arguement as a command line...");
		else {
			n = Integer.parseInt(args[0]);
			for(i=1;i<n;i++){
		    	gcd = gcd(i,n);
		    	if(gcd == 1) //GCD=1 implies numbers are relatively prime
					prime_cnt++;
			}
			System.out.println(prime_cnt);
    	}
	}
}