from collections import defaultdict
N = int(input())
S = list(input())
cnt = [defaultdict(int) for _ in range(3)]
for i,s in enumerate(S):
    cnt[i%3][s] +=1
a = min(cnt[0]['c'],cnt[1]['o'],cnt[2]['n'])
b = min(cnt[0]['o'],cnt[1]['n'],cnt[2]['c'])
c = min(cnt[0]['n'],cnt[1]['c'],cnt[2]['o'])
if a > 0 and b > 0 and c > 0:
    ans = min(a+b+c,N-2)
elif a > 0 and b > 0:
    ans = min(a+b,N-1)
elif a > 0 and c > 0:
    ans = min(a+c,N-1)
elif b > 0 and c > 0:
    ans =min(b+c,N-2)
elif a:
    ans = a
elif b:
    ans = min(b,N-1)
elif c:
    ans= min(c,N-1)
else:
    ans = 0
print(ans)