program step;
var n,q,i,m:integer;
a:array[1..100] of integer;
begin
readln(n);
for i:=1 to n do
read(a[i]);
for i:=1 to n do
begin
if a[i]<a[i+1] then m:=m+(a[i]-a[i+1]) end;
writeln(abs(m));
end.