ans = 10 ** 18

x, y, z, w = map(int, input().split())

for a in range(1, 31):
    for b in range(a + 1, 31):
        for c in range(b + 1, 31):
            dp = [100] * 31
            dp[0] = 0
            for i in range(30 - a + 1):
                dp[i + a] = min(dp[i + a], dp[i] + 1)
            for i in range(30 - b + 1):
                dp[i + b] = min(dp[i + b], dp[i] + 1)
            for i in range(30 - c + 1):
                dp[i + c] = min(dp[i + c], dp[i] + 1)
            tmp = dp[x] + dp[y] + dp[z] + dp[w]
            ans = min(ans, tmp)

print(ans)