var i,j,k,n,t,s,p,z:longint;
a,b:array[0..100000] of longint;
begin
readln(s,t);
for i:=1 to s do
begin
read(n);
for j:=1 to n do
begin
read(a[j]);
p:=p+1;
a[p]:=a[j];
end;
readln;
end;
z:=p;
for p:=1 to z-1 do
for j:=1 to z-p do
if a[j]>a[j+1] then
begin
k:=a[j];
a[j]:=a[j+1];
a[j+1]:=k;
end;
for p:=1 to z do
if a[p]=a[p+1] then
begin
k:=1;
while a[p]=a[p+1] do
begin
k:=k+1;
end;
if k>=t then
begin
write(a[p]);
exit;
end;
end;
write(0);
end.
AAAA
