var n,i,x,y,z,f,b:integer;
a:array[1..1000] 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 x:=x+1;
    if (a[i]<a[i+1]) and (i-1=z) then begin y:=y+(a[i+1]-a[i]); z:=i; end;
    if (a[i]<a[i+1]) and (i>=z+1) and (i-1=b) then begin f:=f+(a[i+1]-a[i]); b:=i; end;
    end;
    if f<y then writeln(y) else writeln(f);

    if x=n then writeln('0');
end.