s = input()
stack = []
cnt = 0
for t in s:
    stack.append(t)
    if t == '<':
        cnt += 1
    elif t == '=':
        pass
    else:
        if cnt:
            if stack[-2] == '=':
                stack.pop()
                while stack[-1] == '=':
                    stack.pop()
                stack.pop()
                cnt -= 1
            else:
                cnt = 0
print(len(stack))