N = int(input())
S = input()
X = [[0] * 3 for _ in range(3)]
for i, c in enumerate(list(S)):
    if c == "c":
        X[i % 3][0] += 1
    if c == "o":
        X[(i - 1) % 3][1] += 1
    if c == "n":
        X[(i - 2) % 3][2] += 1
ans = 0
for i in range(3):
    ans += min(X[i])
print(ans)