* SPICE netlist
A1 N002 0 0 0 N007 0 N004 0 XOR
A2 N004 0 0 0 N009 0 N006 0 XOR
A3 N007 0 0 0 N002 0 N015 0 AND
A4 N009 0 0 0 N004 0 N011 0 AND
A5 N011 0 0 0 N015 0 N013 0 OR
A6 N003 0 0 0 N008 0 N005 0 XOR
A7 N005 0 0 0 N010 0 Sum0 0 XOR
A8 N008 0 0 0 N003 0 N016 0 AND
A9 N010 0 0 0 N005 0 N012 0 AND
A10 N012 0 0 0 N016 0 N014 0 OR
VA0 N003 0 0
VB0 N008 0 0
VCin N010 0 0
A11 N017 0 0 0 N019 0 N018 0 XOR
A12 N018 0 0 0 N014 0 Sum1 0 XOR
A13 N019 0 0 0 N017 0 N022 0 AND
A14 N014 0 0 0 N018 0 N020 0 AND
A15 N020 0 0 0 N022 0 N021 0 OR
VA1 N017 0 1
VB1 N019 0 0
A16 N023 0 0 0 N025 0 N024 0 XOR
A17 N024 0 0 0 N021 0 Sum2 0 XOR
A18 N025 0 0 0 N023 0 N028 0 AND
A19 N021 0 0 0 N024 0 N026 0 AND
A20 N026 0 0 0 N028 0 N027 0 OR
VA2 N023 0 1
VB2 N025 0 1
A21 N029 0 0 0 N031 0 N030 0 XOR
A22 N030 0 0 0 N027 0 Sum3 0 XOR
A23 N031 0 0 0 N029 0 N033 0 AND
A24 N027 0 0 0 N030 0 N032 0 AND
A25 N032 0 0 0 N033 0 Cout 0 OR
VA3 N029 0 1
VB3 N031 0 0
.tran 1

* LTspice schematic (.asc)
Version 4
SHEET 1 2608 2784
WIRE 616 -1392 424 -1392
WIRE 648 -976 552 -976
WIRE 744 -976 648 -976
WIRE -984 -960 -984 -1040
WIRE -824 -960 -984 -960
WIRE -728 -960 -824 -960
WIRE 920 -960 808 -960
WIRE 1000 -960 920 -960
WIRE -552 -944 -664 -944
WIRE -472 -944 -552 -944
WIRE 1304 -944 1064 -944
WIRE -168 -928 -408 -928
WIRE 696 -912 552 -912
WIRE 744 -912 696 -912
WIRE -1144 -896 -1144 -1040
WIRE -776 -896 -1144 -896
WIRE -728 -896 -776 -896
WIRE 968 -896 872 -896
WIRE 1000 -896 968 -896
WIRE -504 -880 -600 -880
WIRE -472 -880 -504 -880
WIRE 872 -816 872 -896
WIRE 872 -816 552 -816
WIRE 968 -816 968 -896
WIRE 1000 -816 968 -816
WIRE -600 -800 -600 -880
WIRE -600 -800 -1224 -800
WIRE -504 -800 -504 -880
WIRE -472 -800 -504 -800
WIRE 1144 -800 1064 -800
WIRE -328 -784 -408 -784
WIRE -1224 -768 -1224 -800
WIRE 1144 -768 1144 -800
WIRE 1176 -768 1144 -768
WIRE -328 -752 -328 -784
WIRE -296 -752 -328 -752
WIRE 920 -752 920 -960
WIRE 1000 -752 920 -752
WIRE 1304 -752 1240 -752
WIRE -552 -736 -552 -944
WIRE -472 -736 -552 -736
WIRE -168 -736 -232 -736
WIRE 696 -720 696 -912
WIRE 744 -720 696 -720
WIRE -776 -704 -776 -896
WIRE -728 -704 -776 -704
WIRE 1176 -704 808 -704
WIRE -296 -688 -664 -688
WIRE 648 -656 648 -976
WIRE 744 -656 648 -656
WIRE -824 -640 -824 -960
WIRE -728 -640 -824 -640
WIRE -168 -512 -168 -736
WIRE -168 -512 -1304 -512
WIRE -1064 -288 -1064 -368
WIRE -904 -288 -1064 -288
WIRE -808 -288 -904 -288
WIRE -632 -272 -744 -272
WIRE -552 -272 -632 -272
WIRE -168 -256 -488 -256
WIRE -1224 -224 -1224 -368
WIRE -856 -224 -1224 -224
WIRE -808 -224 -856 -224
WIRE -584 -208 -680 -208
WIRE -552 -208 -584 -208
WIRE -1304 -128 -1304 -512
WIRE -680 -128 -680 -208
WIRE -680 -128 -1304 -128
WIRE -584 -128 -584 -208
WIRE -552 -128 -584 -128
WIRE -408 -112 -488 -112
WIRE -408 -80 -408 -112
WIRE -376 -80 -408 -80
WIRE -632 -64 -632 -272
WIRE -552 -64 -632 -64
WIRE -152 -64 -312 -64
WIRE -856 -32 -856 -224
WIRE -808 -32 -856 -32
WIRE -376 -16 -744 -16
WIRE -904 32 -904 -288
WIRE -808 32 -904 32
WIRE -152 160 -152 -64
WIRE -152 160 -1288 160
WIRE -1048 384 -1048 304
WIRE -888 384 -1048 384
WIRE -792 384 -888 384
WIRE -616 400 -728 400
WIRE -536 400 -616 400
WIRE -232 416 -472 416
WIRE -1208 448 -1208 304
WIRE -840 448 -1208 448
WIRE -792 448 -840 448
WIRE -568 464 -664 464
WIRE -536 464 -568 464
WIRE -1288 544 -1288 160
WIRE -664 544 -664 464
WIRE -664 544 -1288 544
WIRE -568 544 -568 464
WIRE -536 544 -568 544
WIRE -392 560 -472 560
WIRE -392 592 -392 560
WIRE -360 592 -392 592
WIRE -616 608 -616 400
WIRE -536 608 -616 608
WIRE -168 608 -296 608
WIRE -840 640 -840 448
WIRE -792 640 -840 640
WIRE -360 656 -728 656
WIRE -888 704 -888 384
WIRE -792 704 -888 704
WIRE -168 848 -168 608
WIRE -168 848 -1304 848
WIRE -1064 1072 -1064 992
WIRE -904 1072 -1064 1072
WIRE -808 1072 -904 1072
WIRE -632 1088 -744 1088
WIRE -552 1088 -632 1088
WIRE -248 1104 -488 1104
WIRE -1224 1136 -1224 992
WIRE -856 1136 -1224 1136
WIRE -808 1136 -856 1136
WIRE -584 1152 -680 1152
WIRE -552 1152 -584 1152
WIRE -1304 1232 -1304 848
WIRE -680 1232 -680 1152
WIRE -680 1232 -1304 1232
WIRE -584 1232 -584 1152
WIRE -552 1232 -584 1232
WIRE -408 1248 -488 1248
WIRE -408 1280 -408 1248
WIRE -376 1280 -408 1280
WIRE -632 1296 -632 1088
WIRE -552 1296 -632 1296
WIRE -248 1296 -312 1296
WIRE -856 1328 -856 1136
WIRE -808 1328 -856 1328
WIRE -376 1344 -744 1344
WIRE -904 1392 -904 1072
WIRE -808 1392 -904 1392
FLAG -1144 -1120 0
FLAG -984 -1120 0
FLAG -1224 -688 0
FLAG -1224 -448 0
FLAG -1064 -448 0
FLAG -168 -928 Sum0
FLAG -1208 224 0
FLAG -1048 224 0
FLAG -168 -256 Sum1
FLAG -232 416 Sum2
FLAG -1224 912 0
FLAG -1064 912 0
FLAG -248 1104 Sum3
FLAG -248 1296 Cout
SYMBOL Digital\\xor 792 -1008 R0
SYMATTR InstName A1
SYMBOL Digital\\xor 1048 -992 R0
SYMATTR InstName A2
SYMBOL Digital\\and 776 -752 R0
SYMATTR InstName A3
SYMBOL Digital\\and 1032 -848 R0
SYMATTR InstName A4
SYMBOL Digital\\or 1208 -800 R0
SYMATTR InstName A5
SYMBOL Digital\\xor -680 -992 R0
SYMATTR InstName A6
SYMBOL Digital\\xor -424 -976 R0
SYMATTR InstName A7
SYMBOL Digital\\and -696 -736 R0
SYMATTR InstName A8
SYMBOL Digital\\and -440 -832 R0
SYMATTR InstName A9
SYMBOL Digital\\or -264 -784 R0
SYMATTR InstName A10
SYMBOL voltage -984 -1024 R180
SYMATTR InstName VA0
SYMATTR Value 0
SYMBOL voltage -1144 -1024 R180
SYMATTR InstName VB0
SYMATTR Value 0
SYMBOL voltage -1224 -784 R0
SYMATTR InstName Cin
SYMATTR Value 0
SYMBOL Digital\\xor -760 -320 R0
SYMATTR InstName A11
SYMBOL Digital\\xor -504 -304 R0
SYMATTR InstName A12
SYMBOL Digital\\and -776 -64 R0
SYMATTR InstName A13
SYMBOL Digital\\and -520 -160 R0
SYMATTR InstName A14
SYMBOL Digital\\or -344 -112 R0
SYMATTR InstName A15
SYMBOL voltage -1064 -352 R180
SYMATTR InstName VA1
SYMATTR Value 1
SYMBOL voltage -1224 -352 R180
SYMATTR InstName VB1
SYMATTR Value 0
SYMBOL Digital\\xor -744 352 R0
SYMATTR InstName A16
SYMBOL Digital\\xor -488 368 R0
SYMATTR InstName A17
SYMBOL Digital\\and -760 608 R0
SYMATTR InstName A18
SYMBOL Digital\\and -504 512 R0
SYMATTR InstName A19
SYMBOL Digital\\or -328 560 R0
SYMATTR InstName A20
SYMBOL voltage -1048 320 R180
SYMATTR InstName VA2
SYMATTR Value 1
SYMBOL voltage -1208 320 R180
SYMATTR InstName VB2
SYMATTR Value 1
SYMBOL Digital\\xor -760 1040 R0
SYMATTR InstName A21
SYMBOL Digital\\xor -504 1056 R0
SYMATTR InstName A22
SYMBOL Digital\\and -776 1296 R0
SYMATTR InstName A23
SYMBOL Digital\\and -520 1200 R0
SYMATTR InstName A24
SYMBOL Digital\\or -344 1248 R0
SYMATTR InstName A25
SYMBOL voltage -1064 1008 R180
SYMATTR InstName VA3
SYMATTR Value 1
SYMBOL voltage -1224 1008 R180
SYMATTR InstName VB3
SYMATTR Value 0