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def calculate_points(n, letters):
    num_of_groups = int(n / 10)
    points = 0
    for i in range(0, n, num_of_groups):
        if letters[i:i+num_of_groups] == 'T'*num_of_groups:
            points += 1
    
    return points

n = int(input())
letters = input()

print(calculate_points(n, letters))