E

s2, s1, s = [], [], list(map(int, input().split()))
for i in range(len(s)):
    for j in range(len(s)):
        if i != j:
            s1.append((s[i], s[j], s[i] * s[j]))
for i in range(len(s1)):
    for j in range(len(s1)):
        if i != j and s1[i][0] not in s1[j] and s1[i][1] not in s1[j]:
            s2.append(s1[i][2] + s1[j][2])
print(max(s2))