program operatii;
var n,i,nr1,nr2:longint;
    s:extended;
begin
assign(input,'operatii.in');
reset(input);
read(input,n);
read(input,nr1);
s:=nr1;
for i:=1 to n-1 do begin
    read(input,nr2);
    if nr2>nr1 then s:=s+nr2-nr1;
    nr1:=nr2;
    end;
assign(output,'operatii.out');
rewrite(output);
write(output,s:1:0);
close(output);
end.