var
a,b,i,pocet,x,kon,error,i1,i2,t:integer;
cisla:array[1..7,1..4] of integer;
pole:array[1..100,1..2] of integer;


begin

readln(pocet);
i1:=1;
for i:=1 to pocet do begin
readln(a,b);
if a=b then begin
cisla[a][2]:=cisla[a][2]+1;
end
else begin
cisla[a][1]:=cisla[a][1]+1;
cisla[b][1]:=cisla[b][1]+1;
pole[i1][1]:=a;
pole[i1][2]:=b;
i1:=i1+1;
end;

end;
							{nacitavanie vstupu}

for i:=1 to 6 do begin
if cisla[i][1] mod 2 = 1 then begin kon:=kon+1;
cisla[i][3]:=1;end;
end;							



if (kon=1) or (kon=3) or (kon=4) or (kon=5) or (kon=6)  then error:=1
else begin
if (cisla[1][1]>0) or (cisla[2][1]>0) or (cisla[3][1]>0) or (cisla[4][1]>0) or (cisla[5][1]>0) or (cisla[6][1]>0) then begin

cisla[1][4]:=pole[1][1];
cisla[2][4]:=pole[1][2];
for i:=3 to 6 do begin
i1:=0;
repeat
i1:=i1+1;
until (((pole[i1][1]=cisla[1][4]) or (pole[i1][1]=cisla[2][4]) or (pole[i1][1]=cisla[3][4]) or (pole[i1][1]=cisla[4][4]) or (pole[i1][1]=cisla[5][4]))
 and ((pole[i1][2]<>cisla[1][4]) and (pole[i1][2]<>cisla[2][4]) and (pole[i1][2]<>cisla[3][4]) and (pole[i1][2]<>cisla[4][4]) and (pole[i1][2]<>cisla[5][4]))) or
(((pole[i1][2]=cisla[1][4]) or (pole[i1][2]=cisla[2][4]) or (pole[i1][2]=cisla[3][4]) or (pole[i1][2]=cisla[4][4]) or (pole[i1][2]=cisla[5][4])) and
((pole[i1][1]<>cisla[1][4]) and (pole[i1][1]<>cisla[2][4]) and (pole[i1][1]<>cisla[3][4]) and (pole[i1][1]<>cisla[4][4]) and (pole[i1][1]<>cisla[5][4]))) or (i1>pocet);



writeln(pole[i1][1],'',pole[i1][2]);



if ((pole[i1][1]=cisla[1][4]) or (pole[i1][1]=cisla[2][4]) or (pole[i1][1]=cisla[3][4]) or (pole[i1][1]=cisla[4][4]) or (pole[i1][1]=cisla[5][4])) and (i1<=pocet) then cisla[i][4]:=pole[i1][2]
else if i1<=pocet then cisla[i][4]:=pole[i1][1];
end;







for i:=1 to 6 do begin
i1:=0;
if cisla[i][1]>0 then begin
repeat
i1:=i1+1;
until (cisla[i1][4]=i) or (i1>6);
if i1>6 then error:=1;
end;







end;


end
else begin
for i:=1 to 6 do
if cisla[i][2]>0 then i1:=i1+1;
if i1>1 then error:=1
else
i:=0;
repeat
i:=i+1;
until cisla[i][2]>0;
x:=i;

if error=1 then writeln('Neda sa')
else begin writeln('Da sa');

if kon=2 then begin
i:=0;
repeat
i:=i+1;
until cisla[i][3]=1;
a:=cisla[i][3];
repeat
i:=i+1;
until cisla[i][3]=1;
b:=cisla[i][3];




i:=0;
repeat
i:=i+1;
until (pole[i][1]=b) or (pole[i][2]=b);
pole[pocet+1][1]:=pole[i][1];
pole[pocet+1][2]:=pole[i][2];
pole[i][2]:=0;						{oznacenie konca}
pole[i][1]:=0;





if cisla[a][2]>0 then
for i:=1 to cisla[a][2] do write(a,'',a,' ');
i:=0;
repeat
i:=i+1;
until (pole[i][1]=a) or (pole[i][2]=a);
if pole[i][1]=a then begin
write(pole[i][1],'',pole[i][2],' ');
x:=pole[i][2];
end
else begin
write(pole[i][2],'',pole[i][1],' ');
x:=pole[i][1];
end;
pole[i][1]:=0;
pole[i][2]:=0;						{vypisanie prvych cisel}
end;




							

if x=0 and then begin
i:=0;
repeat
i:=i+1;
until cisla[i][1]>0;
x:=i;
end;							{ak nie je udany zaciatok (kon=0)}

if (cisla[1][1]+cisla[2][1]+cisla[3][1]+cisla[4][1]+cisla[5][1]+cisla[6][1]) div 2 -1>0 then
for i:=1 to (cisla[1][1]+cisla[2][1]+cisla[3][1]+cisla[4][1]+cisla[5][1]+cisla[6][1]) div 2 -1 do begin

i1:=0;
repeat
i1:=i1+1;
until (pole[i1][1]=x) or (pole[i1][2]=x);
if pole[i1][1]=x then begin
write(pole[i1][1],'',pole[i1][2],' ');
x:=pole[i1][2];
end
else begin	
write(pole[i1][2],'',pole[i1][1],' ');
x:=pole[i1][1];
end;
pole[i1][1]:=0;	
pole[i1][2]:=0;

if cisla[x][2]>0 then
for i2:=1 to cisla[x][2] do
write(x,'',x,' ');
end
else

if cisla[x][2]>0 then
for i2:=1 to cisla[x][2] do
write(x,'',x,' ');	





end;









readln;
end.