var i,g,w,a,b,c,min:integer;
   f,e:text;       nul,ok:boolean;         v,j:array [1..100] of integer;
BEGIN
assign(f,'energii.in');reset(f);assign(e,'energii.out');rewrite(e);
readln(f,g);readln(f,w);ok:=false;nul:=false; c:=10001;
IF (G>1) and (G<1001) and (W>1) and (W<5001) THEN
BEGIN
for i:=1 to g do
   begin
    readln(f,a,b);v[i]:=a;j[i]:=b;
   end;
for i:=1 to g do
  if (v[i]>=10001) or (j[i]>=10001) or (v[i]<1) or (j[i]<1) then
   begin
    nul:=true;ok:=true;
   end;
  if nul=false then
   begin
    for i:=1 to g do
     if v[i]>=w then ok:=true;
     if ok=true then
    for i:=1 to g do
     BEGIN
      a:=v[i];b:=j[i];
      if (a>=w) and (b<c) then
       begin
        c:=b;min:=a;
       end;
    END;
if ok=false then write(e,-1);
if ok=true then write(e,c);
close(f);close(e);
END;
END;
END.