var
i,kol,n,m,k1,k2:integer;
reb,a:array[1..100,1..100]of integer;
ver:array[1..100]of integer;
procedure def_s(k1:integer);
var
i,j,n1,k:integer;
pr,q:array[1..100]of integer;
begin
for i:=1to n do pr[i]:=0;
i:=1;n1:=1;pr[k1]:=1;q[1]:=k1;

while(i<=n1)do begin
k:=q[i];
for j:=1to n do
if(a[k,j]>0)and (pr[j]=0)then begin
n1:=n1+1;
q[n1]:=j;
pr[j]:=k;
if (ver[k]=0) and (ver[j]=0) then begin ver[k]:=1;ver[j]:=1;kol:=kol+1;
reb[kol,1]:=k;reb[kol,2]:=j end;
end;
i:=i+1;
end;
end;

begin
readln(n,m);
for i:=1to m do begin
readln(k1,k2);
a[k1,k2]:=1;
a[k2,k1]:=1;
end;
def_s(1);
writeln(kol);
for i:=1to kol do writeln(reb[i,1],' ',reb[i,2]);
end.

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