S = list(input())
N = len(S)
stack = list()
f = 0 #先頭に<があるか
for i in range(N):
    if S[i]==">" and f:
        ok = False
        while True:
            p = stack.pop()
            if p=="=":
                ok = True
            if p=="<" and ok:
                break
            elif p=="<":
                stack.append(p)
                stack.append(">")
                f = 1
                break
        f -= 1
    elif S[i]==">":
        f = 0
        stack.append(S[i])
    elif S[i]=="<":
        f += 1
        stack.append(S[i])
    else:
        stack.append(S[i])
#print(stack)
print(len(stack))