program alex;
var f:text;
    e:boolean;
    k,i,n,z,max,s:longint;
    a,b:array[1..100000]of longint;
begin
assign(f,'heavymetal.in');reset(f);
readln(f,n);
for i:=1 to n do
    readln(f,a[i],b[i]);
close(f);
k:=1;
e:=false;
while e=false do
      begin
      e:=true;
      for i:=1 to n-k do
          if a[i]>a[i+1] then begin
                              z:=a[i];
                              a[i]:=a[i+1];
                              a[i+1]:=z;
                              z:=b[i];
                              b[i]:=b[i+1];
                              b[i+1]:=z;
                              e:=false;
                              end;
      k:=k+1;
      end;
i:=1;
repeat
max:=b[i];
while a[i+1]=a[i] do
      begin
      i:=i+1;
      if b[i]>max then max:=b[i];
      end;
s:=s+max-a[i];
while a[i]<max do
      i:=i+1;
until(i>n);
assign(f,'heavymetal.out');rewrite(f);
writeln(f,s);
close(f);
end.