S = input()

open = 0
stack = []
for c in S:
    if c == '<':
        open += 1
        stack.append(c)
    elif c == '=':
        stack.append(c)
    else:
        if open == 0 or stack and stack[-1] == '<':
            stack.append(c)
            open = 0
            continue
        while stack and stack[-1] == '=':
            stack.pop()
        assert stack and stack[-1] == '<'
        stack.pop()
        open -= 1
print(len(stack))