n=int(input())
s=input()
s0=s[0::3]
s1=s[1::3]
s2=s[2::3]
con=min(s0.count("c"),s1.count("o"),s2.count("n"))
nco=min(s0.count("n"),s1.count("c"),s2.count("o"))
onc=min(s0.count("o"),s1.count("n"),s2.count("c"))
if con==n:
  print(n)
else:
  print(min(con+nco+onc,n-1))