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

g0 = s[::3]
g1 = s[1::3]
g2 = s[2::3]

def count_chars(g):
    c = o = nn = 0
    for char in g:
        if char == 'c':
            c += 1
        elif char == 'o':
            o += 1
        elif char == 'n':
            nn += 1
    return (c, o, nn)

c0, o0, n0 = count_chars(g0)
c1, o1, n1 = count_chars(g1)
c2, o2, n2 = count_chars(g2)

max_con = 0
len_N = n

for a in range(3):
    if a == 0:
        c = c0
        o = o1
        nn = n2
    elif a == 1:
        c = c1
        o = o2
        nn = n0
    else:
        c = c2
        o = o0
        nn = n1
    max_a = min(c, o, nn, len_N)
    max_con += max_a

print(max_con)