program mwt;
var
    ans:extended;
    a:array[0..50000,1..2]of extended;
    key:array[1..50000]of longint;
    w:array[1..50000]of extended;
    n,i:longint;
procedure sort(l,r,lab:longint);
var
    i,j,x,t:longint;
begin
    if l>=r then exit;
    i:=l;j:=r;
    x:=key[(l+r)shr 1];
    repeat
        while a[key[i],lab]<a[x,lab] do
           i:=i+1;
        while a[key[j],lab]>a[x,lab] do
           j:=j-1;
        if i<=j then
          begin
                t:=key[i];key[i]:=key[j];key[j]:=t;
                i:=i+1;j:=j-1;
           end;
    until i>j;
    sort(l,j,lab);
    sort(i,r,lab);
end;
procedure jie(x:longint);
var
    i:longint;
    l,r,sl,sr,min:extended;
begin
    for i:=1 to n do
       key[i]:=i;
    sort(1,n,x);
    l:=0;r:=0;
    sl:=0;sr:=0;
    for i:=2 to n do
       begin
            sr:=sr+w[key[i]];
           r:=r+(a[key[i],x]-a[key[1],x])*w[key[i]];
      end;
   min:=r;
   for i:=2 to n do
     begin
         sl:=sl+w[key[i-1]];
         l:=l+sl*(a[key[i],x]-a[key[i-1],x]);
           r:=r-sr*(a[key[i],x]-a[key[i-1],x]);
           sr:=sr-w[key[i]];
           if l+r<min then min:=l+r;
      end;
   ans:=ans+min;
end;
begin
    assign(input,'ballc.in');
    reset(input);
    assign(output,'ballc.out');
    rewrite(output);
    readln(n);
    for i:=1 to n do
      read(w[i]);
    for i:=1 to n do
      readln(a[i,1],a[i,2]);
    ans:=0;
    jie(1);
    jie(2);
    write(ans:0:2);
    close(input);
    close(output);
end.