Var i,n:longint;
l,r,k:extended;
x,y:array [1..15000] of extended;
function f(k:extended):extended;
Var rez:extended;
i:longint;
begin
  rez:=0;
  for i:=1 to n do
  rez:=rez+sqrt(y[i]*y[i]+(x[i]-k)*(x[i]-k));
  f:=rez;
end;
begin
  Assign(input,'input.txt'); reset(input);
  Assign(output,'output.txt'); rewrite(output);
  read(n);
  for i:=1 to n do
  read(x[i],y[i]);
  l:=x[1];
  r:=x[2];
  for i:=1 to 500 do
  begin
    k:=(r-l)/3;
    if f(l+k)>f(l+k+k)
    then l:=l+k
    else r:=l+k*2;
  end;
  writeln(r);
end.

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