N=list(map(int,input()))
n=len(N)

def solve(i,p):
	global a,A
	if p==1:
		for j in range(i+1,n):
			if v[j]==0 and N[j]!=N[i]:
				v[j]=1
				solve(j,2)
	if p==2:
		for j in range(i+1,n):
			if v[j]==0 and N[j]==N[i]:
				v[j]=1
				solve(j,3)
	if p==3:
		a+=1
		A=max(A,a)
		for j in range(n):
			if v[j]==0:
				v[j]=1
				solve(j,1)
		a-=1
	return

a=0
A=0
v=[0]*n
v[0]=1
for i in range(n):
	if N[i]!=0:
		solve(i,1)

print(A)