S = input()
stack = []
for s in S:
    if s != '>':
        stack.append(s)
    else:
        if not stack or stack[-1] != '=':
            stack.append(s)
        else:
            # '='をとれるだけとる
            l = []
            while stack and stack[-1] == '=':
                l.append(stack.pop())
            
            # 最後が'<'ならとる
            if stack and stack[-1] == '<':
                stack.pop()
            else:
                stack.extend(l)
                stack.append(s)

print(len(stack))