import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()

dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = (1 << 63)-1
# inf = (1 << 31)-1
md = 10**9+7
# md = 998244353

n = II()
s = SI()
t = "con"

cnt = [[0]*3 for _ in range(3)]
for si in range(3):
    for i in range(si, 3*n, 3):
        c = t.find(s[i])
        if c == -1: continue
        cnt[si][c] += 1
# p2D(cnt)

ans = 0
aa = []
for si in range(3):
    cur = n-1 if si else n
    for j in range(3):
        i = (si+j)%3
        cur = min(cur, cnt[i][j])
    aa.append(cur)

if aa[0] == n:
    ans = n
else:
    ans = min(n-1, sum(aa))

print(ans)