S=input()
ans=[]
left=0
for i in S:
	ans.append(i)
	if i=="<":
		left+=1
	elif i==">" and left:
		if ans[-2]=="<":
			left=0
			continue
		left-=1
		ans.pop()
		while ans[-1]=="=":
			ans.pop()
		ans.pop()
print(len(ans))