module std_tb;reg [7:0] a,b,c,d;wire [7:0]  ra,rb,rc,rd; range sort4(ra,rb,rc,rd,a,b,c,d);initial fork  a=15;  b=56;  c=23;  d=24;  #50 a=5;  #50 b=10;  #50 c=1;  #50 d=4;  #86 a=15;  #15 b=51;  #87 c=86;  #59 d=23;  #100 $stop;  join  endmodule