const maxn=500;

var m,n,h,t:integer;

at:array[0..maxn,0..maxn]of boolean;

p,st:array[0..maxn]of integer;

hs:array[0..maxn]of boolean;

///////////////

procedure add(x:integer);

var i:integer;

begin

inc(t);

p[t]:=x;

st[x]:=st[p[h]]+1;

hs[x]:=false;

if x=n then

begin

write(st[x]-1);

halt;

end;

end;

///////////////

procedure init;

var i,j,k:integer;

a:array[0..maxn]of integer;

begin

fillchar(at,sizeof(at),false);

readln(m,n);

for i:=1 to m do

begin

j:=0;

while not(eoln) do

begin

inc(j);

read(a[j]);

for k:=1 to j-1 do

at[a[k],a[j]]:=true;

end;

readln;

end;

end;

///////////////

procedure main;

var i:integer;

begin

fillchar(hs,sizeof(hs),true);

t:=1; h:=0;

p[1]:=1; st[1]:=0; hs[1]:=false;

while h<t do

begin

inc(h);

for i:=1 to n do

if at[p[h],i] and hs[i] then add(i);

end;

end;

///////////////

procedure print;

begin

write('NO');

end;

///////////////

begin

init;

main;

print;

end.