def is_cpctf_like(s5):
    return (
        s5[0] == s5[2] and
        len(set([s5[0], s5[1], s5[3], s5[4]])) == 4
    )

def count_cpctf_like_substrings(s):
    n = len(s)
    count = 0
    for i in range(n - 4):
        sub = s[i:i+5]
        if is_cpctf_like(sub):
            count += 1
    return count

# Read input
N = int(input())
S = input().strip()

# Output the result
print(count_cpctf_like_substrings(S))