A=[4,10,15,20]
B=[1,13,29]
C=[5,14,28]
A.sort(),B.sort(),C.sort()
i=0
j=0
k=0
t=-1
An=len(A)
Bn=len(B)
Cn=len(C)
Max=0
Min=min_dif=99999
while i<An and j<Bn and k<Cn:
    if A[i]>Max:
        Max=A[i]
    if B[j]>Max:
        Max=B[j]
    if C[k]>Max:
        Max=C[k]
    if A[i]<Min:
        Min=A[i]
        t=1
    if B[j]<Min:
        Min=B[j]
        t=2
    if C[k]<Min:
        Min=C[k]
        t=3
 
 
    if Max-Min < min_dif:
        min_dif=Max-Min
        min_i=i
        min_j=j
        min_k=k
 
    if t==1:
        i=i+1
    if t==2:
        j=j+1
    if t==3:
        k=k+1
    Max=0
    Min=99999
print "A=",A[min_i]," B=",B[min_j]," C=",C[min_k]," min diff=",min_dif
 

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