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:
n = int(raw_input())

list1 = []
for i in range(0, n):
    a = int(raw_input())
    b = raw_input()
    total = 0
    total1 = 0
    
    c = 'GB'
    for j in range(0, a+a, 2):
        if b[j] != c[0]:
            total += 1
        if b[j+1] != c[1]:
            total += 1
    c = 'BG'        
    for j in range(0, a+a, 2):
        if b[j] != c[0]:
            total1 += 1
        if b[j+1] != c[1]:
            total1 += 1
    if total1 > total:       
        list1.append(total/2)
    else:
        list1.append(total1/2)

for i in list1:
    print i