module keypad(valid, number, a, b, c, d, e, f, g);
    output  valid;
    output [3:0] number;
    input   a, b, c, d, e, f, g;
    wire ad, cd, be, af, cf, bd, ce, ae, bf, bg;

    //buttons
    and a0(bg, b, g); //0
    and a1(ad, a, d); //1
    and a2(bd, b, d); //2
    and a3(cd, c, d); //3
    and a4(ae, a, e); //4
    and a5(be, b, e); //5
    and a6(ce, c, e); //6
    and a7(af, a, f); //7
    and a8(bf, b, f); //8
    and a9(cf, c, f); //9

    //valid
    or o(valid, ad, bd, cd, ae, be, ce, af, bf, cf, bg);

    //number[0]
    or o2(number[0], ad, cd, be, af, cf);

    //number[1]
    or o3(number[1], bd, cd, ce, af);

    //number[2]
    or o4(number[2], ae, be, ce, af);

    //number[3]
    or o5(number[3], bf, cf);

endmodule // keypad