from collections import deque

S = input()

dq = deque([])
l = 0
for i in range(len(S)):
    if S[i] == "<":
        l += 1
        dq.append(S[i])
    elif S[i] == ">":
        if l > 0 and dq[-1] == "=":
            while True:
                x = dq.pop()
                if x == "<":
                    l -= 1
                    break
        else:
            l = 0
            dq.append(S[i])
    else:
        dq.append(S[i])

print(len(dq))