program ballc;
var
  ans:extended;
  data:array [0..100000,1..2] of extended;
  w:array [1..100000] of extended;
  p:array [1..100000] of longint;
  n,i:longint;
procedure qsort(a,b,no:longint);
var
  i,j,s,t:longint;
begin
  if a<b then begin
    i:=a;j:=b;
    s:=p[(a+b) div 2];
    repeat
      while data[p[i],no]<data[s,no] do inc(i);
      while data[p[j],no]>data[s,no] do dec(j);
      if i<=j then begin
        t:=p[i];
       	p[i]:=p[j];
       	p[j]:=t;
        inc(i);
        dec(j);
      end;
    until i>j;
    qsort (a,j,no);
    qsort (i,b,no);
  end;
end;
procedure get(no:integer);
var
  i:longint;
  suma,sumb,a,b,min:extended;
begin
  fillchar (p,sizeof(p),0);
  for i:=1 to n do p[i]:=i;
  qsort (1,n,no);
  a:=0;b:=0;suma:=0;sumb:=0;
  for i:=2 to n do begin
    b:=b+w[p[i]]*(data[p[i],no]-data[p[1],no]);
    sumb:=sumb+w[p[i]];
  end;
  min:=b;
  for i:=2 to n do begin
    suma:=suma+w[p[i-1]];
    a:=a+suma*(data[p[i],no]-data[p[i-1],no]);
    b:=b-sumb*(data[p[i],no]-data[p[i-1],no]);
    sumb:=sumb-w[p[i]];
    if a+b<min then min:=a+b;
  end;
  ans:=ans+min;
end;
begin
  assign (input,'ballc.in');
  reset (input);
  assign (output,'ballc.out');
  rewrite (output);
  fillchar (data,sizeof(data),0);
  fillchar (w,sizeof(w),0);
  readln (n);
  for i:=1 to n do read (w[i]);
  for i:=1 to n do readln (data[i,1],data[i,2]);
  close (input);
  ans:=0;
  get(1);get(2);
  writeln (ans:0:2);
  close (output);
end.