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:
'''
 Read input from stdin and provide input before running code

name = raw_input('What is your name?\n')
print 'Hi, %s.' % name
'''
t= int(raw_input())
while(t):
	n=input()
	odr = raw_input()
	arr=[]
	arr1=[]
	arr2=[]
	count1=0
	count2=0
	le = len(odr)
	for i in range(le):
	    if (odr[i]=="G"):
	        arr.append(1)
	    else:
	        arr.append(-1)
	for i in range(le):
	    if i%2==0:
	        arr1.append(1)
	        arr2.append(-1)
	    else:
	        arr1.append(-1)
	        arr2.append(1)
	
	for i in range(le):
	    if(arr[i]+arr1[i]==0):
	        count1=count1+1
	    if(arr[i]+arr2[i]==0):
	        count2=count2+1
	print min(count1,count2)/2
	t=t-1