import sys
input = sys.stdin.readline
from collections import *

N = int(input())
S = input()[:-1]
c = [0, 0, 0]
o = [0, 0, 0]
n = [0, 0, 0]

for i in range(3*N):
    if S[i]=='c':
        c[i%3] += 1
    elif S[i]=='o':
        o[i%3] += 1
    elif S[i]=='n':
        n[i%3] += 1

ans = 0
now = 0

for _ in range(min(c[0], o[1], n[2])):
    if now+3<=3*N:
        now += 3
        ans += 1
    
now += 1

for _ in range(min(c[1], o[2], n[0])):
    if now+3<=3*N:
        now += 3
        ans += 1
    
now += 1

for _ in range(min(c[2], o[0], n[1])):
    if now+3<=3*N:
        now += 3
        ans += 1

print(ans)