v0, v1, v2, v3 = map(int, input().split())

MAX = 31
ans = 999

for a in range(1, MAX):
    for b in range(a + 1, MAX):
        for c in range(b + 1, MAX):
            dp = [MAX] * 999
            dp[0] = 0
            for i in range(MAX - a):
                dp[i + a] = min(dp[i + a], dp[i] + 1)
            for i in range(MAX - b):
                dp[i + b] = min(dp[i + b], dp[i] + 1)
            for i in range(MAX - c):
                dp[i + c] = min(dp[i + c], dp[i] + 1)

            ans = min(ans, dp[v0] + dp[v1] + dp[v2] + dp[v3])

print(ans)