Problem: Xenny was a teacher and his class consisted of N boys and N girls. He took all his students to the playground and asked them to stand in a straight line. The boys and the girls formed a perfect line, but Xenny seemed unhappy. He wanted them to form an alternating sequence of boys and girls, i.e., he wanted that after a boy, there should be a girl in the line, and vice-versa.

In order to form an alternating sequence, a boy and a girl could swap their positions.

Given the original sequence in which the boys and girls were standing, find the minimum number of swaps required to form an alternating sequence.

Note: An alternating sequence can start either with a boy or a girl.

Input
First line of input consists of a natural number T - the number of testcases.
T testcases follow. For each testcase:

First line consists of a single integer N - the number of boys, and the number of girls.
Second line consists of a string of length 2N, representing the original sequence.
In this string, a boy is represented by uppercase character B and a girl by G.

Output
For each testcase, print the minimum number of swaps required to get an alternating sequence on a new line.

Constraints
1 ≤ T ≤ 5

1 ≤ N ≤ 10^6

SAMPLE INPUT
1
2
BBGG

SAMPLE OUTPUT
1

Explanation

The first boy from left  can swap his position with the first girl from right to get the sequence:

GBGB

This is an alternating sequence and it was obtained using 1 swap.

Solution (in PYTHON):

Solution:
def swaps(arng,reqarng):
	count = 0 
	for i in range(len(arng)):
		if arng[i]!=reqarng[i]:
			count = count + 1
	return count/2


t = int(input())
for i in range(t):
	n = int(input())
	arng = raw_input()
	for j in range(2*n):
		if j==0:
			reqarng = "B"
		else:
			if j%2==0:
				reqarng = reqarng + "B"
			else:
				reqarng = reqarng + "G"
	s1 = swaps(arng,reqarng)
	s2 = swaps(arng,reqarng[::-1])
	if s1>s2:
		print s2
	else:
		print s1