S=input().strip()
ans = len(S)
stack = []
for s in S:
    if s=="<":
        stack.append(1)
    elif s=="=":
        if stack:
            stack[-1] += 1
    else:
        if stack:
            if stack[-1]>1:
                ans-=stack.pop()+1
            else:
                stack.clear()
print(ans)