n = int(input())
s = input().strip()

# Initialize counts for 'c', 'o', 'n' in each of the three groups (0, 1, 2)
c = [0, 0, 0]
o = [0, 0, 0]
n_ = [0, 0, 0]

for i in range(len(s)):
    group = i % 3
    char = s[i]
    if char == 'c':
        c[group] += 1
    elif char == 'o':
        o[group] += 1
    elif char == 'n':
        n_[group] += 1

# Calculate the maximum possible 'con' substrings
max_con = min(c[0], o[1], n_[2]) + min(c[1], o[2], n_[0]) + min(c[2], o[0], n_[1])

print(max_con)