from collections import defaultdict

def solve():
    N=int(input())
    S=input()

    A=[defaultdict(int), defaultdict(int), defaultdict(int)]

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

    ans=0
    p,q,r="con"
    for _ in range(3):
        ans+=min(A[0][p], A[1][q], A[2][r])
        p,q,r=q,r,p

    if ans==N and A[0]["c"]<N:
        ans-=1

    return ans

print(solve())