from collections import *
from itertools import *
from functools import cache, partial
from pprint import pprint
import sys
from typing import Any, Final

try:
    from icecream import ic
except ImportError:  # Graceful fallback if IceCream isn't installed.
    ic = lambda *a: None if not a else (a[0] if len(a) == 1 else a)  # noqa
debug = partial(print, file=sys.stderr)
dpprint = partial(pprint, stream=sys.stderr)
sys.setrecursionlimit(10**6)
MOD = 998244353

S_ = input()
N = len(S_)
S = []
cnt = 0
for s in S_:
    if s == "<" or s == ">":
        if cnt > 0:
            S.append(("=", cnt))
            cnt = 0
        S.append((s, 1))
    else:
        cnt += 1

if cnt > 0:
    S.append(("=", cnt))
# ic(S)

ans = N
stack = []
for char, cnt in S:
    if char in ["<", ">"]:
        stack.append((char, cnt))
    elif stack and stack[-1][0] == "=":
        _, cnt2 = stack.pop()
        stack.append(("=", cnt + cnt2))
    else:
        stack.append(("=", cnt))
    while (
        len(stack) >= 3
        and stack[-1][0] == ">"
        and stack[-2][0] == "="
        and stack[-3][0] == "<"
    ):
        ans -= 2 + stack[-2][1]
        stack.pop()
        stack.pop()
        stack.pop()

print(ans)