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n = int(input())
tests = input()

points = 0
group_size = n // 10
count = 0
i = 0

while i < n:
    if tests[i] == 'T':
        count += 1
        if count == group_size:
            points += 1
            count = 0
        i += 1
    else:
        i += (group_size - count)
        count = 0
print(points)