x,y,z,w=map(int,input().split())
ANS=1<<30

for i in range(1,31):
    for j in range(i+1,31):
        for k in range(j+1,31):
            DP=[1<<31]*(100)

            DP[0]=0

            for l in range(31):
                DP[l+i]=min(DP[l+i],DP[l]+1)
                DP[l+j]=min(DP[l+j],DP[l]+1)
                DP[l+k]=min(DP[l+k],DP[l]+1)

            ANS=min(ANS,DP[x]+DP[y]+DP[z]+DP[w])

print(ANS)