f(f(y,f(y,f(y,x))),f(x,f(y,z))) = x.  % C_1
f(f(y,f(y,f(x,y))),f(x,f(z,y))) = x.  % C_2
f(f(y,f(y,f(x,x))),f(x,f(z,y))) = x.  % C_3
f(f(y,f(y,f(x,z))),f(x,f(z,y))) = x.  % C_4
f(f(y,f(y,f(z,x))),f(x,f(y,z))) = x.  % C_5
f(f(y,f(f(x,y),y)),f(x,f(y,z))) = x.  % C_6
f(f(y,f(y,f(y,x))),f(x,f(z,y))) = x.  % C_7
f(f(f(f(y,x),y),y),f(x,f(z,y))) = x.  % C_8
f(f(f(f(y,x),z),z),f(x,f(y,z))) = x.  % C_9
f(f(f(y,f(y,x)),y),f(x,f(z,y))) = x.  % C_10
f(f(f(y,f(x,x)),y),f(x,f(z,y))) = x.  % C_11
f(f(f(f(y,x),z),z),f(x,f(z,y))) = x.  % C_12
f(f(f(f(y,x),y),y),f(x,f(y,z))) = x.  % C_13
f(f(f(y,f(x,z)),y),f(x,f(y,z))) = x.  % C_14
f(f(f(y,f(z,x)),y),f(x,f(y,z))) = x.  % C_15
f(f(f(y,f(y,x)),y),f(x,f(y,z))) = x.  % C_16