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
        else:
            A[i%3]["x"]+=1

    c,o,n,x="conx"
    ans=0

    p,q,r=c,o,n
    for t in range(3):
        x=min(A[0][p],A[1][q],A[2][r])
        if t!=0:
            x=min(x,N-1)
        ans+=x
        p,q,r=q,r,p
    return ans

print(solve())