n = int(input())
s = input()
from collections import defaultdict
d0 = defaultdict(int)
d1 = defaultdict(int)
d2 = defaultdict(int)

for i in range(n):
    d0[s[3*i]] += 1
    d1[s[3*i+1]] += 1
    d2[s[3*i+2]] += 1

ans = 0

l = ["c","o","n"]
ans1 = min(d0["c"],d1["o"],d2["n"])
ans2 = min(d0["n"],d1["c"],d2["o"])
ans3 = min(d0["o"],d1["n"],d2["c"])

if ans1 == n:
    print(n)
    exit()

ans = ans1+ans2+ans3

if ans == n:
    print(ans-1)
    exit()

print(ans)