program cz2011_3;
const maxn=100000;
var
f:array[1..maxn]of longint;
stack:array[1..maxn,1..2]of longint;
n,i,j,h,t,last,x,s:longint;

begin
read(n);
for i:=1 to n do read(f[i]);
stack[1,1]:=1;stack[1,2]:=n;
last:=2;
while last>1 do begin
last:=last-1;
h:=stack[last,1];t:=stack[last,2];
i:=h;j:=t;x:=f[h];
while i<j do begin
while (i<j) and (f[j]<x) do j:=j-1;
if i<j then begin
f[i]:=f[j];i:=i+1;
end;
while (i<j) and (f[i]>x) do i:=i+1;
if i<j then begin
f[j]:=f[i];j:=j-1;
end;
end;
f[i]:=x;
if (h<i-1) then begin
stack[last,1]:=h;stack[last,2]:=i-1;last:=last+1;
end;
if (i+1<t) then begin
stack[last,1]:=i+1;stack[last,2]:=t;last:=last+1;
end;
end;
s:=f[2]-f[1];
for i:=3 to n do s:=s+f[i]-f[i-1];
writeln(s);
end.
输入1：
3
20 10 30

输入2：
10
40 36 47 29 25 35 22 42 13 58

输出：-20|-45