>>151

A(a,b,c,d)
 = A(A(a,b,c)、A(b,c,d)、A(c,d,a)、A(d,a,b))
 ≧ G(A(a,b,c)、A(b,c,d)、A(c,d,a)、A(d,a,b))
 = G(A(A(a,b),A(b,c),A(a,c)) 、A(A(b,c),A(b,d),A(b,d))、A(A(a,c),A(a,d),A(c,d))、A(A(a,b),A(a,d),A(b,d)))
 ≧ G(G(A(a,b),A(b,c),A(a,c)) 、G(A(b,c),A(b,d),A(b,d))、G(A(a,c),A(a,d),A(c,d))、G(A(a,b),A(a,d),A(b,d)))
 = G(A(a,b)、A(a,c)、A(a,d)、A(b,c)、A(b,d)、A(c,d))
 ≧ G(G(a,b)、G(a,c)、G(a,d)、G(b,c)、G(b,d)、G(c,d))
 = G(a,b,c,d)