var s:int64;
        n,n1,n2,i:longint;
begin
assign(input,'operatii.in');
reset(input);
read(input,n);
read(input,n1);
s:=n1;
for i:=1 to n-1 do begin
read(input,n2);
if n2>n1 then
s:=s+n2-n1;
n1:=n2;
end;
assign(output,'operatii.out');
rewrite(output);
write(output,s);
close(output);
end.