N=int(input())*3
S=input()
C=[[0,0,0],[0,0,0],[0,0,0]]
T='con'
for i in range(N):
  for j in range(3):
    if T[j]==S[i]:
      C[(i-j)%3][j]+=1
D=[min(C[i]) for i in range(3)]
v=0
x=[]
for i in range(3):
  for j in range(D[i]*3):
    x.append(i)
  x.append(-1)
x=x[:N]
P=[0]*3
for i in range(min(N,len(x))):
  if x[i]>=0:
    P[x[i]]+=1
print(P[0]//3+P[1]//3+P[2]//3)