#!/usr/bin/env python3
# %%
import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

# %%
N = int(readline())
S = read().rstrip().decode()


# %%
def test(n, alphabets, word):
    """alphabetsを使ってwordより真に大きいものをn個つくれる"""
    if n <= 0:
        return True
    if not word:
        return len(alphabets) >= n
    w = word[0]
    while alphabets and alphabets[-1] > w:
        alphabets.pop()
        n -= 1
    if n <= 0:
        return True
    if len(alphabets) < n:
        return False
    if alphabets[-n] < w:
        return False
    return test(n, alphabets[:-n], word[1:])


# %%
A = sorted(S)
left = 0
right = N + 1
while left + 1 < right:
    x = (left + right) // 2
    if test(x, A[:], 'yuki'):
        left = x
    else:
        right = x


# %%
print(left)