S = input()

st = []
ans = len(S)
for i,s in enumerate(S):
    if s == "<":
        st.append(0)
    elif s == "=":
        if st:
            st[-1] += 1
    else:
        if not st:
            continue
        if st[-1] == 0:
            st.clear()
        else:
            ans -= st.pop()+2

print(ans)