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

# Initialize counts for each group
g0_c = g0_o = g0_n = 0
g1_c = g1_o = g1_n = 0
g2_c = g2_o = g2_n = 0

for i in range(len(s)):
    c = s[i]
    g = i % 3
    if c == 'c':
        if g == 0:
            g0_c += 1
        elif g == 1:
            g1_c += 1
        else:
            g2_c += 1
    elif c == 'o':
        if g == 0:
            g0_o += 1
        elif g == 1:
            g1_o += 1
        else:
            g2_o += 1
    elif c == 'n':
        if g == 0:
            g0_n += 1
        elif g == 1:
            g1_n += 1
        else:
            g2_n += 1

# Calculate contributions from each starting group
contrib0 = min(g0_c, g1_o, g2_n)
contrib1 = min(g1_c, g2_o, g0_n)
contrib2 = min(g2_c, g0_o, g1_n)

total = contrib0 + contrib1 + contrib2
print(total)