from collections import *

N = int(input())
S = list(input())
D = [defaultdict(int) for i in range(3)]
for i in range(3*N):
    D[i%3][S[i]] += 1

L = [0, 0, 0]
L[0] = min(D[0]["c"], D[1]["o"], D[2]["n"])
L[1] = min(D[0]["n"], D[1]["c"], D[2]["o"])
L[2] = min(D[0]["o"], D[1]["n"], D[2]["c"])

# print(L)
# print(D)
ans = 0
N *= 3
if N >= 3 * L[0]:
    ans += L[0]
    N -= 3 * L[0] + 1
    N = max(0, N)
else:
    print(ans + N//3)
    exit()
if N >= 3 * L[1]:
    ans += L[1]
    N -= 3 * L[1] + 1
    N = max(0, N)
else:
    print(ans + N//3)
    exit()
    
if N >= 3 * L[2]:
    ans += L[2]
    N -= 3 * L[2] + 1
    N = max(0, N)
else:
    print(ans + N//3)
    exit()

print(ans)