6)

//return the maximum of integers x and y.
int max(int x, int y)
{
	return x>y?x:y;
}
// find the maximum value in the n- element.
//integer array a.
int arraymax(int a[], int n)
{
	//in a one element array the maximum is a[0]
	//stopping condition.
	if(n==1)
		return a[0];
	else
	//recursive step, find the maximum of a[n-1] and 
	//arraymax(a, n-1)
	return max(arraymax(a, n-1),a[n-1]);
}

//determine if the string is a palindrome. s is the starting index and e is 
// the ending index.
int pal(char A[], int s, int e)
{
	// if s and e are equal, A is a palindrome. This is the stopping condition.
	if(s>=e)
		return 1;
	else
	//if A[s] and A[e] are not equal A is not a palindrome.
	if(A[s]!= A[e])
		return 0;
	else
		// test the string between indices s+1 and e-1
	return pal(A, s+1, e-1)
}

//recursively computes the GCD of m and n.
int gcd(int a, int b)
{
	int remainder= a%b;

	if (remainder==0)
		return b;
	else
		return gcd(b, remainder);
}