en2asc = lambda x: ord(x) - ord("a")

N = int(input())
S = input()
ct = [0] * 26
for i, s in enumerate(S):
    ct[en2asc(s)] += 1

ans = 0

_y = en2asc("y")
_u = en2asc("u")
_k = en2asc("k")
_i = en2asc("i")

# yuki[a-h]
for i in range(_i):
    add = min(ct[_y], ct[_u], ct[_k], ct[_i], ct[i])
    ans += add
    ct[_y] -= add
    ct[_u] -= add
    ct[_k] -= add
    ct[_i] -= add
    ct[i] -= add

# yukii
add = min(ct[_y], ct[_u], ct[_k], ct[_i] // 2)
ans += add
ct[_y] -= add
ct[_u] -= add
ct[_k] -= add
ct[_i] -= add * 2

# yukj
add = min(ct[_y], ct[_u], ct[_k], ct[en2asc("j")])
ans += add
ct[_y] -= add
ct[_u] -= add
ct[_k] -= add
ct[en2asc("j")] -= add

# yukk
add = min(ct[_y], ct[_u], ct[_k] // 2)
ans += add
ct[_y] -= add
ct[_u] -= add
ct[_k] -= add * 2

# yu[l-t]
for i in range(_k + 1, _u):
    add = min(ct[_y], ct[_u], ct[i])
    ans += add
    ct[_y] -= add
    ct[_u] -= add
    ct[i] -= add

# yuu
add = min(ct[_y], ct[_u] // 2)
ans += add
ct[_y] -= add
ct[_u] -= add * 2

# y[v-x]
for i in range(_u + 1, _y):
    add = min(ct[_y], ct[i])
    ans += add
    ct[_y] -= add
    ct[i] -= add

# yy
add = ct[_y] // 2
ans += add
ct[_y] -= add * 2

# z
add = ct[en2asc("z")]
ans += add
ct[en2asc("z")] -= add

print(ans)