import re
n = int(input())
s = input()
# p1 = [m.span() for m in re.finditer('CPC', s)]
p2 = [m.span() for m in re.finditer('CPCTF', s)]
p3 = [m.span() for m in re.finditer('CPCTCPC', s)]
print(len(p2) + len(p3))