def main():
    v0, v1, v2, v3 = map(int, input().split())
    ans = float('inf')
    max = 31
    for a in range(1, max):
        for b in range(a + 1, max):
            for c in range(b + 1, max):
                dp = [float('inf')] * max
                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)
    
if __name__ == '__main__':
    main()