import sys
input = lambda :sys.stdin.readline()[:-1]
ni = lambda :int(input())
na = lambda :list(map(int,input().split()))
yes = lambda :print("yes");Yes = lambda :print("Yes");YES = lambda : print("YES")
no = lambda :print("no");No = lambda :print("No");NO = lambda : print("NO")
#######################################################################


n = ni()
s = input()

a = [0,0,0]
for i in range(n):
    if s[i*3] == "c":
        a[0] += 1
    if s[i*3+1] == "o":
        a[1] += 1
    if s[i*3+2] == "n":
        a[2] += 1
x1 = min(a)
if min(a) == n:
    print(n)
    exit()

a = [0,0,0]
for i in range(n):
    if s[i*3] == "o":
        a[0] += 1
    if s[i*3+1] == "n":
        a[1] += 1
    if s[i*3+2] == "c":
        a[2] += 1
x2 = min(a)


a = [0,0,0]
for i in range(n):
    if s[i*3] == "n":
        a[0] += 1
    if s[i*3+1] == "c":
        a[1] += 1
    if s[i*3+2] == "o":
        a[2] += 1
x3 = min(a)

print(min(x1+x2+x3, n-1))