type arr=array[1..50000]of longword;
var n,k,i,maxx,nk:longint;a,b:arr;max:longword;c:array[1..50000]of 1..50000;
procedure qsort(l,r:longint);
var i,j,m,p:longint;
begin
i:=l;j:=r;m:=a[l];
repeat
while a[i]<m do inc(i);
while a[j]>m do dec(j);
if i<=j then
begin
p:=a[i];a[i]:=a[j];a[j]:=p;p:=b[i];b[i]:=b[j];b[j]:=p;
p:=c[i];c[i]:=c[j];c[j]:=p;inc(i);dec(j);
end;
until i>j;
if l<j then qsort(l,j);
if i<r then qsort(i,r);
end;
begin
readln(n,k);
for i:=1 to n do begin readln(a[i],b[i]);c[i]:=i;end;
qsort(1,n);
max:=b[n];maxx:=n;
nk:=n-k+1;
for i:=n downto nk do
if b[i]>max then
begin
max:=b[i];
maxx:=i;
end;
writeln(c[maxx]);
end.