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

# Initialize counts for 'c', 'o', 'n' in each group (0, 1, 2)
counts = [{'c': 0, 'o': 0, 'n': 0} for _ in range(3)]

for idx in range(len(s)):
    group = (idx + 1) % 3  # Determine group based on 1-based index
    c = s[idx]
    if c in ['c', 'o', 'n']:
        counts[group][c] += 1

# Calculate the maximum possible 'con' for each type
type0 = min(counts[0]['c'], counts[1]['o'], counts[2]['n'], n - 1)
type1 = min(counts[1]['c'], counts[2]['o'], counts[0]['n'], n)
type2 = min(counts[2]['c'], counts[0]['o'], counts[1]['n'], n - 1)

print(type0 + type1 + type2)