from collections import defaultdict

n = int(input())
S = list(input())

C = [defaultdict(int) for _ in range(3)]
for i in range(3 * n):
    C[i % 3][S[i]] += 1
ANS = []
for i in range(3):
    ANS.append(min(C[i % 3]['c'], C[(i + 1) % 3]['o'], C[(i + 2) % 3]['n']))
ans = sum(ANS)
if ans == n:
    if ANS[0] != n:
        ans -= 1
print(ans)